Buy scrolls of spells you'll use occasionally. Plane Shift, for example. All spells that I have noted are better cast by wizards fall into scroll territory.
Buy wands of spells you'll use a lot, but don't want to waste spells known on.
Make sure the spells in your wands are not Save or X spells, nor rely heavily on a high caster level for effectiveness.
Of course, any Sorcerer worth the title knows his limited spell list means he needs an extra supply of scrolls and wands to make up his lack of knowledge. Here's a few wands I've found useful...
* First off, recall the disadvantage of wands: it uses a base caster level rather than yours, and can only be up to 4th level spells.
* Second, the DC's do *NOT* take into account your primary casting stat. So don't bother with Save or Screwed spells, they'll never land.
* It has 50 charges, so only wand it if you plan on doing it a LOT, otherwise just grab a couple of scrolls.
With this in mind, you don't want wands that have a lot of level-dependent stuff. That means, unfortunately, a lot of your 'blaster' spells. However, there are some very useful utility spells to pick up as wands:
Grease. No level-dependent effects, and no SR to worry about. Flat DC balance check. It's always good for a few laughs. If you don't know it, DO wand it.
Summon Monster I. Surprisingly handy utility. Use it to trip traps, walk into dubious areas wherein you suspect might be hazardous, to experiment with unknown substances...
Ray of Enfeeblement. Handy at low levels, not so much at higher levels. No save, and not much in the way of level-dependent stuff. If you like using it a lot, wand it.
Expeditious Retreat. What you do when something does close with you. At least until you can afford Dimension Door.
Knock. Wand this, because caster level is irrelevant. And you never know when your skillmonkey isn't skilled enough.
Glitterdust. If you don't learn it, wand it. It points out invisible things.
Web. Good battlefield control, has a use even if they make the save.
Mirror Image. Really, you should have this as a Known spell, so you shouldn't need to wand it. If, for some reason, you decide to NOT pick it up, Wand it, and smack yourself in the head for not learning it.
(animal)'s (stat). If your party wants buffing, ask them to buy you the wands. This makes them think twice about calling you a worthless buff-bot.
Rope Trick. It would be expensive to get it as cast by an 8th level caster (12,000 by my calculations), but hey, that's an awful lot of adventuring days you don't need to worry about being ambushed.
Silence. Use it in the area effect version that doesn't allow save. Follow up with a method of keeping them in the area. Nerfs opponent casters.
Rings of Protection are always good
Rings of Spell Turning are great for defense against other casters.
Rings of Freedom of Movement means you don't have to fear grappling monks, ever.
Rings of X Ray Vision... have applications not appreciated by people who do not ware lead lined clothing.
Twilight Mythral Feycraft OMGTWFBBQ Chain Shirt of Heavy Fortification.
It is a pain to write on our character sheet, but it is a chain shirt that is wearable, and give you immunity to critical hits and sneak attack.
It is a great thing to have... but does it make anyone else feel dirty to own a piece of equipment whose name is longer than that of several real world countries combined?
Never mind, it isn't core either. Now, a Mithral Buckler of Heavy Fortification is, so grab that instead.
Rod of Absorption - Absorb spells, and use the energy to cast more spells. A good buy.
Rod of Cancellation - Crafted by Fox News, this rod is a one shot affair that Disjunctions any magic item it touches. Might be useful.
Immovable Rod - As with the Decanter of Endless Water, this is a fun item with many uses. Everyone loves an Immovable Rod!
Rod of Lordly Might - Best pickup line ever.
Rod of Wonder - Pure win. Almost as dangerous to you as it is to your enemies.
Core sorcerers cannot use Quicken Spell, but a Rod of Maximize really helps out with Enervations. Widen Spell, Enlarge Spell, and other minor metamagic feats are can be had as Rods, but aren't necessarily worth it.
Then again, Disintegrating someone from over 800 feet away can be rather nice....
Bracers of Armor: Better than Mage Armor, but it won't stack with your Chain Shirt of OMGWTFBBQness.
Decanter of Endless Water: It won't improve your casting per se, but it is always a fun item to have, and will foil your DM's plotting with a bit of ingenuity and a knowledge of fluid physics. (Hint: Pressure= Density*acceleration due to gravity*depth)
Handy Haversack, Bag of Holding: These types of things make up for a Sorcerer's lack of carrying capacity.
Hand of Glory: Ah, the Hand of Glory. Insert a candle and it gives light only to the holder! Best friend of thieves and plunderers! Your have fine taste, sir.
The best part is that it allows you to add an extra ring slot. A bargain for everyone who likes rings; normally, you'd have to either use an epic feat to free up some ring space or... get creative down under.
Ehlonna's Quiver (Efficent Quiver). Surprisingly useful. What, you don't use bows and arrows? No, but a Wand is the same size as an arrow, so you can carry all your wands around with easy access. Rods go in the Javelin slot, and Staves go in the Bow slot.
Glove of Storing. If you're not getting the Dexterity, this can be used to always make sure you've got a wand on-hand. (Not to self: Stab Shneeky to death for pun.)
Cloak of Charisma/Gloves of Dexterity/Amulet of Health: Use is obvious
Cloak of Etherealness: Good item, if you don't have the spell, but if you want to use it, you have to give up the Cloak of Charisma.
Cloak of Resistance: Good for making sure you don't die as easily, but same problem as above.
Ioun Stones: the Orange Ioun stone increases your caster level by +1, for a hefty price. Get it.
The ones that absorb spells are also pretty useful. Grab as many as you want and proceed to give children you meet astronomy lessons.
Marvelous Pigments: Paint your way out of trouble! Finally, Art majors can do something useful. (warning: For the sake of your sanity and mine, keep these the hell away from Dalai, Picasso, Gaugan, and anyone associated with them.)
Robe of the Archmagi: The armor, caster level check and resistance bonuses are nice. The SR will be ineffectual at the level you get it, unless you go around beating up lesser casters a lot.
Scarab of Protection
The scarab’s possessor gains spell resistance 20. The scarab can also absorb energy-draining attacks, death effects, and negative energy effects. Upon absorbing twelve such attacks, the scarab turns to powder and is destroyed.
An excellent way of avoiding a Finger of Death to the face. Doesn't stack with the Amulet of Health, though.
Tome of X: Increases X stat by 1-5 points. You know which one to increase.