3 Armor Choices: Archmage's Robes, Master Robe of Destruction, Master Robe of Restoration & Ward Absorb Restoration Perk. Remember, Wards can absorb spiders poison shots, chaurus poison shoots, dragon breathes and turn them into magicka. Atronach Alteration Perk and Atronach Stones? you can't choose when enable them, and they can absorb Durnehviir wasting 300 seconds of your Thu'um.
Must Ring: Ring of the Erudite (from Volkihran Vampires Side Quest Rings of Blood Magic)
Must Food: Elsewyr Fundue (Ale, Eidar Cheese Wheel, Moon Sugar)
Must Potion: Magicka Potency (300 seconds 100 Fortify Magicka Regen)
Good: Aetherial Crown can store Atronach Stone so you can choose when turn it on or off. If so Apprentice stone give Morokei magicka bonus and you get both mage standing stone bonuses. Also you wear a Crown!
Good: Amulet of Talos and Blessing of Talos. Up to 60% Faster Shout Recovery all togheter with Dragon Aspect. 1 Yol/Fo every 12 seconds! 1 Fus every 6 seconds! Perma Mass Stagger: Fus, Ice Storm, Ice Storm, Fus, Ice Storm, Ice Storm
enchanted magicka gloves and enchanted fire/frost/shock resists boots
enchanted skyforge steel dagger of absorb magicka and lightning damage (Highest Magicka Absorb for you, High Magicka Burn to enemies, close to no weight and Low Stamina Cost)
I don't understand why everyone suggest heavy armor on mages, I think you must move fast. Also I think a shield is more important than an armor. Also light and heavy armor cost 10 perks, mage armor cost only 3 perks on mages. Also Magic Resistances share Perk Tree with Mage Armor.