Ummm......I'm going to go out on a limb here and say shoes.

I wear Dark Brotherhood shrouded boots.

I always forget about this, and then I get random light armor skill ups. Is there any disadvantage to wearing light armor gloves/shoes/boots (or heavy for that matter, though I wouldn't do that) as a mage?

I usually wear the footwraps you already have on your character the moment you start. It suits the entire magic/mysterious persona. Then again, I usually wear Leather braces and boots to protect myself more and to level up my Light Armour skill somewhat.

Levitation sandals?

I'm pretty sure the test is randomly generated. You can buy the spell as someone else stated. Or, if you're not powerfull enough at that moment in time to cast the required spell reload and see if the spell has changed to something you can do.

On topic. Boots! I wear boots. I have quite the collection.

My character would've done the usual hippy cliche of liking nothing but the feel of the earth beneath her feet etc but it's not quite such a cunning idea when the icy landscape would freeze her toes off. So warm, furry boots, however much it offends her sensibilities.