Yep, high-alchemy is always a good fast choice for leveling your magic. You never fail, and if you can make one or more of the materials yourself, then you'll probably end up making a decent profit. If you want cheap, effortless, albeit boring levels, go ahead and try failing curses. I'm sure you've heard of the method. Get your mage bonus as low in the negatives as you can (full metal armour, etc.), and get to cursing on something that can't hit you. Preferably these would be behind a wall or some other obstruction. Finally you could go for Fire Striking with Chaos Gauntlets at Steel Dragons... Not always profitable, not the fastest, but if you can get lucky with a pair of legs (or even a skirt), you could more than make up for your expenses.