Bare feet are ideal when you practice yoga and actually serve a dual purpose. First, you need to have traction for the standing poses so that you wont slip. Second, working without shoes helps you fully exercise and articulate your feet. An exception to this would be if you doing a practice on a cold floor and you need socks for warmth.
You do not need any special clothing for yoga, but what you wear must be comfortable, warm but not too warm, and allow the maximum range of movement. Clothing such as: leotards, cotton tights, bike shorts, loose Tshirts or tank tops would be good. Bulky or overly loose clothing will only get in the way. If you have long hair tie it back, so it does not interfere with your asanas. Keep a sweater close by in case you start to feel cold.