Depends, as a mage you really do not need to wear Heavy or even Leather armors because of your Alteration perks.
Generally you should aim for getting the Arch-Mages robe and put around 5-6 perks into Alteration school, which will increase the defence of your alteration buffs x3-4 times, if you aren't wearing anything else except for robes, those spells will give you same armor or even greater armor than if you were actually wearing really good heavy armor and you can still retain your bonuses from the robe, tiara, and ring.
Also you don't really need to use enchantment to create your armors because you can't put up extra enchants on robes that already have options on them (although I am not sure if you still can't when you have level 100 enchanting, as it provides the ability to put 2 enchants on a piece of equipment)
Although if you want to go the heavy armor path and enchant them with mana regen, then you will have to heavily level up enchant (to lv100) and put a lot of perks into the tree, about 10 perks or something like that, but you will not be able to benefit from Alteration perks much tho and even if you have a fully upgraded perk tree for Enchantment, I'm still not sure if you will be able to actually achieve full benefits that an Archmage or any other Major magic school robe provides.
EDIT: This answer said you won't benefit from levelling up light/heavy armor masteries, which I can't agree to. The only mean of levelling in this game is pretty much spamming skills, the more spells you have levelled up - the greater your general level will be and more perks you will have available.
Having those levelled up a bit will only benefit your general level.