If you wish to level up, you have to do two things:
- use your major skills. If one of your major skills is blade for instance, you have to do a lot of sword fighting to level up. In your case, you probably want to use whatever schools of magic your character has as major skills as much as possible
- to actually level up, you have to sleep. Not wait, sleep. You can only do that on a bed or a bedroll
Hope that helps

Being good means getting better.