I'm a bit disappointed with alteration as a formerly unarmored mage. I'm sure going completely unarmored and depending on the perk that triples alteration shields is viable, even in Master, but it feels a hell of a lot less powerful than having a good set of light or heavy armor that you've enchanted yourself. I don't need the magicka regen from robes if I can chant all my armor so that destruction spells cost next to nothing. Plus if I go that route, I'll have permanent armor rating on me at all times without having to cast a shield, and the shield is just a bonus. This is before I've even gotten the perk to double enchant things. It'll be ridiculous by that point.
I'm not sure what they could even do to fix this. Sure, you can enchant your own robes, but to do that you have to get a robe that doesn't already have the -cost +regen on it, and that defeats the purpose of wearing them, other than just being able to.
In conclusion, screw robes and circlets. Go unarmored if it's your character's flavor, but it's not recommended. I'd be interested in counter experiences/arguments, but I'm not expecting to find any. There seems to be a consensus here on the power of crafting and enchanting - they're very powerful. And you can't craft anything that's considered unarmored except jewelry.
So I've been playing a pure mage... What should I do?
I know how you feel there. I'd suggest switching. You'll be far more effective. The alteration unarmored perk feels like an afterthought more than something that
works. I'm wearing a heavy armor mask and light armor everywhere else. You don't need to put perks into armor for it to be decent, or at least I haven't.