What's the best build for a pure Mage? Only ES game I played was Oblivion, once and I don't remember anything :-( --- There is only one god and his name is Death. And there is only one thing we say to Death. Not today.
Basically anything that doesn't solely have melee bonuses, so almost any races. Personally, I think High Elf is better suited for hybrids over pure mages, since bonus magicka makes a bigger difference to a character that has more focus on health and stamina, rather than just magicka.
On the other hand, reducing damage you take or abilities that interfere with enemies directly attacking you might be worth considering.