For 100% pure mages I would pick High Elf because you have +50 Magicka which includes an initial bonuses:
+10 Illusion
+5 Alteration, Conjuration, Destruction, Enchanting, Restoration
Additional Spell: Fury
For your powers: Highborn Regenerate magicka 25x faster for 60 seconds, once per day
Depending if you're using a PC to play Skyrim you can install a mod to which gives you unlimited race usages