If I have full light armor, and a shield up, which is also a light shield, will my light armor skill rise or just block?

You must take damage for it to raise your armor skill.

Blocking does not mitigate damage 100% so..

From what I've read. Your shield just raises block. You can use a heavy shield and still get the light matched armor bonus.

I believe its both block and armor but I'm not 100% sure.

If you get hit it raises armor, if you block or bash it raises block.

If you can restore your health easily, just let some wolves or weak creatures beat up on you while you heal up. One of the things I like in Skyrim is that you don't have to repair armor or weapons after heavy use like you did in the previous TES games.

What im asking is if I just take hits while afk with a shield up, as long as im taking some damage, will it raise my armor skill or just block?

No, Blocking raises Block. You must take an unblocked hit to raise your armor.

Let a Giant hit you if you can survive the blow. Heal up. Repeat. Every hit pretty much levels your armor.

Block does not raise light armor. You have to get hit. The harder you are hit the faster light armor raises. Master light armor trainer in Riften, she is the rude vendor in the center of town.

The damage absorbed seems to give you your skill up... so you want to wear best armor available (absorbs more) and take as many hits as you can. I find any powerleveling kind of pointless in this game. You don't need a high skill to be "ready" for anything. If it doesn't come somewhat naturally for your character, you simply don't need it.