I know right? This doesn't seem like a question that needs to be asked.
I guess I will answer the call.
There are two ways that I would do this.
a) Prioritize for 100s in Destruction, Conjuration, and Restoration and break the game
-or-

Prioritize for 100s in all the above and Enchanting, then enchant yourself an outfit than makes your conjuration and destruction spells free to cast - resulting in breaking the game even harder.
....you can probably guess that I don't play as a mage anymore due to lack of challenge, and boredom arises before I even hit 40.
Edit: High Elf with Mage Stone
Mages guild obvious, and companions guild. Push comes to shove, werewolf power helps.