The Good the Bad and the Monk, a 5e Monk guide
I'm not going to explain why you would play a monk, or what the role of a monk is. This is just about the choices for a monk, and made for people who already decided that they're going to play a monk.
1. Colors
2. Stats
3. Backgrounds
4. Features
5. Monastic Traditions
6. Multiclassing
Spoiler: Colors
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Gold This is perfect, the best choice in almost every build
Sky blue This is very good to have, also nice for most builds
Blue Solid choice, it's maybe not the best but it's not bad
Black This is decent, it's not optimal but you’re not hindering your character picking this.
Purple Maybe sometimes useful, but very often you're wasting valuable character growth.
Red Just nope. There’s either something strictly better or it’s a downright awful pick.
Spoiler: Stats
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STR As Monk you're often in melee, and athletics is nice, but you don't really need it
DEX Your most important stat, for AC, damage rolls and attack rolls
CON Hit points and constitution saving throws are both important, but constitution is for a monk less important than wisdom or dexterity, don't overrate it.
INT The dump stat in 5e, maybe you want it higher than strength but if you have a wizard or other high int character there's no reason for that.
WIS Very important for AC and DCs, it has to reach 18 or 20 at higher levels.
CHA Nice for skill checks, if you have two or more people with high charisma in your party, this even becomes RED
Spoiler: Races
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Hilldwarf Put a 14 in CON and never look back. +1 wisdom is also very nice. If you begin at higher levels this becomes sky blue, but you really need a DEX of 16.
Moutaindwarf +2 constitution and +2 strength isn't that bad, but with low wisdom and dexterity you won't be a really good monk.
High elf At least you have the dexterity bonus, features like trance aren't bad
Wood elf +2 Dex and +1 Wis, oh yeah, extra speed is nice. In addition, the basic elf features and Mask of the Wild which is very useful.
Drow A high elf with sunlight sensitivity.
Stout halfling Good bonuses, lucky, brave. The low speed becomes less of a problem later.
Lightfoot halfling Close to blue, you have all the nice halfling features and +2 dex, but you're not way better than a high elf.
Human Boring but useful, you can have 16 dex, 16 wis, 14 con at first level and you don't have to dump the other stats that hard.
Variant human 16 dexterity, 16 wisdom and a feat... A perfect race, as monks are pretty MAD andyou need every ASI in wisdom or dexterity (maybe one in CON), now you can also have a feat. Your best option.
Dragonborn You have a breath weapon and a resistance, that's all.
Rock gnome As I said before, dexterity and wisdom are very important for monks. The spell advantage is nice but not enough to warrant picking this race.
Forest gnome With +1 dex, you can have a solid monk. This is almost blue, and you still have the spell advantage.
Half-elf The +1 wisdom and +1 dexterity are nice. Half-elf is a good choice for everybody. Close to blue, but it's still just decent.
Half-orc +1 constitution and some other features. Not red but not even close to black.
Tiefling Useless ability bonuses and magic reliant on your dump stat.
Elemental evil:
Aarakocra Flying speed, Dexterity, wisdom, this is sky blue and nothing less.
Deep Gnome Not that different from forest gnomes.
Air genasi Not bad, this is good for most monks, and it's the only genasi with a DEX bonus.
Earth genasi A sneaky mountain dwarf.
Fire genasi Inteligence is your dump stat, don't take this subrace.
Water genasi The constitution and wisdom bonuses make up for your lack of dexterity. This becomes blue if you start at a higher level.
Goliath A bad half-orc. Don't take it.
Spoiler: Backgrounds
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Acolyte Typical monk proficiencies but religion isn't a great skill, insight is still useful.
Charlatan You don't need sleight of hand or deception.
Criminal Stealth is very useful and makes this way better than charlatan. The tool proficiencies, however, aren't that good.
Entertainer Acrobatics is nice, disguise kit isn't bad either. However, performance and an instrument aren't what you need.
Folk hero Two wisdom skills and average tool proficiencies, close to blue.
Guild artisan You don't need persuasion, but all other things this gives you are good to have.
Hermit Typical monk, medicine and the discovery feature are both useful.
Noble History, Persuasion, a gaming set? Not what you're looking for.
Outlander Everyone likes athletics, and I'm sure you'll find some uses for Survival. A good feature and decent equipment make this a good choice.
Sage Even worse than noble.
Sailor Great skills and a great feature. The best background for most classes, and that includes monk.
Soldier Decent. Not a lot more to say here.
Urchin The skills might not be required often, but at least they use dexterity. If your party lacks a rogue, consider this.
Spoiler: Features
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Unarmored defense You can't use armor or shields, so this is a great thing to have. Not gold because a level in barbarian/dragon sorcerer would give you about the same.
Martial arts The reason you are a monk.
Ki Without this, you are a fighter with bad damage output. With it, you are a monk.
Unarmored movement Improved mobility. Not a lot else to say.
Deflect missiles This will only apply in certain situations, but when it does you'll be thankful you have it.
Ability score improvement Monks are MAD, so ASI's are good.
Slow fall Sometimes, this will safe your life. Other times, you forget all about it. In my opinion, it is more useful than deflect missiles, but still close to black
Extra attack As expected for a martial class.
Stunning strike Stunning can be quite powerful, but note it'll cost you a lot of ki points. By the time enemies are getting legendary resistance and high CON saves, this becomes a bit worse. Note that you can apply this on all attacks you make in a round.
Ki-Empowered Strikes Pretty much required to have if you want to remain useful in combat. In a campaign without magic items, this becomes even better.
Evasion I'm pretty sure I don't have to say how useful this can be.
Stillness of mind Charmed and Frightened aren't too uncommon effects. Being able to remove them is good, although it costs you an action.
Purity of Body Poison is common, but you'll still not use this 90% of the time.
Tongue of the Sun and Moon A social ability, which gives you some out-of-combat versatility. It won't safe your life, but it can make certain encounters far easier.
Diamond soul Rerolling (death) saving throws is great on its own. Proficiency in all saving throws on top of that? This is great, and nothing else.
Timeless body If you are still worried about starving to death at this level, something has gone wrong. The other features are mere fluff.
Empty Body Astral projection on yourself only isn't what I'd exactly call useful. The other feature is great, though. Even against enemies with truesight this is sky blue.
Perfect self Not that great compared to some other level 20 features (druid, barbarian).
Spoiler: Monastic Traditions
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Way of the Open Hand Best of the three, this makes you more effective in combat than any other monk.
Open hand technique Simply amazing.
Wholeness of body Free healing, but it costs an action.
Tranquility Nearly unusable. A level one spell you cannot even control? Awful.
Quivering Palm This is simply wonderful. It amounts to a save-or-die, which 5e doesn't have many of.
Way of the Shadow Not bad, if you have/want a stealthy party this is something for you. Shadow step and Opportunist both make you stronger in combat.
Shadow Arts More and better spells than the elemental monk.
Shadow Step This must be the best feature of this tradition.
Cloak of Shadows A surprise attack. It is nice, but nothing more.
Opportunist Who doesn't like free damage?
Way of the Four Elements Spellcasting from a rather limited list, and it consumes the ki points you badly need.
Breath of Winter Your normal attacks do more damage and don't cost ki points.
Clench of the North Wind Stunning strike is better.
Elemental Attunement This is better than it appears to be. A lot can be done with this power. Note that you can technically swap it out at a higher level.
Eternal Mountain Defense Not too bad, but from level 18 on Empty Body is better.
Fangs of the fire snake Good damage, and the extra reach opens up hit-and-run tactics. You could pick worse.
Fist of Four Thunders Battlefield control is good. Open Hand is better at throwing a single person around, though.
Fist of Unbroken Air Just attack, you'll do more damage.
Flames of the Phoenix Fireball is a good spell, but you don't need more ways to deal damage that badly.
Gong of the Summit Bad damage for 3 ki points...
Mist Stance Both out-of-combat and in-combat use.
Ride the Wind Mobility is good. This spell gives mobility. This spell is good.
River of Hungry Flame Lots of uses, depends on your creativity.
Rush of the Gale Spirits I can only see one or two situations where you would use this
Shape the Flowing River Depends on how much your DM is willing to let slide.
Sweeping Cinder Strike This is simply awful.
Water Whip Errata turned this into an action, making it worthless.
Wave of Rolling Earth Just like wall of fire, this can be used in many ways.
Spoiler: Multiclassing
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Barbarian Extra rage damage and unarmored defense are useless, but rage gives other benefits, and Reckless Attack is pretty neat.
Bard A spellcasting class that needs your dump stat. If you have a Charisma of 14 or more (why would you?), this becomes decent. If your charisma is 10 or less, though, this is simply awful
Cleric You already have good wisdom, and many of the domains have attractive powers.
Druid Druid/Monk is a well-known multiclass. Extra AC while wildshaping and spells, and all you need are stats you'd boost anyway? Better than cleric, except for a one-level dip. Some options with the wild shape won't work, ask your DM before you go for Druid, maybe you DM says you don't get the extra AC (or attacks/spells).
Fighter One or two levels in fighter rarely hurt.
Paladin Maybe take two levels so that you get LoH and Divine Smite.
Ranger Ignore the stat matchups; this is a bad multiclass.
Rogue Shadow monk mixes nice with rogue.
Sorcerer Why would you do this?
Warlock This rating might come as a surprise, but truth is bladelock/monk builds can get rather interesting. There are still better options, though.
Wizard Same as sorcerer.
Spoiler: Feats
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Alert This is good for every class, not sure if this is the ASI worth but not a bad choice at all
Athlete You can't do many things with this, when you reach level 9 this becomes even red
Actor Probably you have a low charisma, maybe for roleplaying (changeling monk) but not a good option for most builds
Charger Can be useful, not worse for you than for most other classes
Crossbow Expert You don't have the proficiency with a hand crossbow, ignoring loading is the only you can do with this. When you reach level 11 your monk weapons already do 1d8 (shortbow) and this becomes worthless
Defensive Duelist If you use shortsword(s) this isn't bad
Dual Wielder Useless, just useless
Dungeon Delver In some campaigns nice, in most not worth it
Durable You have an average constitution, this makes you after every short rest ready for fights
Elemental adept If you are an elemental monk you often don't want damage spells, so Always red
Grappler If you have high strength this feat isn't as bad as it sounds
Great Weapon Master Nothing for you
Healer If there isn't a healing bard/cleric/druid/paladin this becomes blue. This feat isn't bad at all.
Heavily Armored You don't need armor
Heavy Armor Master You don't wear heavy armor, because you're a monk...
Inspiring Leader with a high charisma this feat isn't as bad as most feats, with a charisma of 13 or lower you really can't use this.
Keen Mind Boosts inteligence, you don't need that. And the benefits are too situational
Lightly Armored Don't wear armor
Linguist As keen mind, but a little bit better
Lucky This is so useful, even when you get diamond soul this stays blue
Mage Slayer Depending on campaign, but now you have good defenses against spellcasters. In melee you are already a boss and against archers you have deflect missiles.
Magic Initiate Maybe for hex, but magic initate is a little bit UP feat.
Martial adept This is worse than magic initate, because you here don't get cantrips
Medium armor master I said enough about armor
Mobile Extra speed and some other helpful things. Perfect for a monk
Moderately Armored Armor...
Mounted Combatant Decent feat if you have a mount, but you are faster than you mount so maybe not. A higher levels this is still black, but not as good as it was
Observant +1 wisdom and other good abilities, nice for an odd stat in wisdom.
Polearm master Even with a quarterstaff this is just bad
Resillent Good for constitution or wisdom, but when you reach level 14 you can't use this at all
Ritual Caster Pretty bad
Savage attacker If you are damage focussing and you have still an ASI, you can use this
Sentinel You already use your bonus action, and you already are faster than most enemies
Sharpshooter Makes you better ranged, but if you want to go ranged why did you become a monk? Conclusion: Not for monks
Shield Master A shield? For monks?
Skilled There are some nice skills for you
Skulker For shadow monks this is blue
Spell Sniper For elemental monks this is also a waste of your ASI
Tavern Brawler +1 stat and a little bit better in grappeling. Other features you already have
Tough Good for the hit points, but you also need the consitution save, becomes blue if you get diamond soul
War Caster Like elemental adept and spell sniper, also red for elemental monks
Weapon Master Because they don't count as a monk weapon, you can't use it
Thanks to Dire_Stirge for helping me out with this guide!