Assuming you are talking about a form of Archery where you are shooting at people with padded arrows, and not actual combat.
The best thing you can wear is something that covers as much of your body as possible, while still allowing you to move freely. Jeans and a long-sleeved shirt are a good option, or you could wear light armor if you have it. You will also want to wear gloves to protect your hands from the string, and eye protection to keep the arrows from hitting your face.