The Elder Scrolls: It's the IX Divines, you milk-drinkers

[veti]

Yes, that works out if I'd leveled illusion first. Except I'm now almost level 80. All the opponents are capped out and very few of them are low level enough to affect with illusion without perks. And perks are so hard to come by now! Sounds way fun if I'd focused in it at first, but I sadly didn't.

You should at least have 'Muffle', I generally find two or three tomes of that by the time I'm half that level. Repeatedly casting that will level illusion pretty fast, even if there's no in-game reason to cast it.

Once your skill gets up to 60 or so, you should be able to buy Invisibility.

Another way to practise is to use Calm spells on civilians - the area-effect version, cast on a crowd, also levels illusion very quickly, and has no bad effects. (Careful with the 'Courage' spells - those can, in some cases, cause otherwise-peaceful people to turn violent.)

As for perks - I recommend cheating the mod "Trade Dragon Souls for Perks".