RayRay
Wal-Mart if you want inexpensive, but their sizes always run big so if you're really skinny, everything will probably be too big. Nike has good workout clothes but they're not cheap, but they fit better (hence the reason they're more expensive but hey, I'd rather spend a little more and have it fit better) Goody's might have something. They're not too expensive and they have an okay fit. Hope I helped.

icarlx15
Always go with Soffe shorts. They are cute, comfy, and the guys think they are adorable. They come in all colors! Go to your loccal sports authority or modells or even a Dick's sporting goods. Any of those will work. I play lacrosse and I wear an extra small too! I'm very skinny as well. Also wear athletic T-shirts with long tank tops that stick out the bottom. Good luck, and I hope this helped!

Joe
shorts - tops - Hope this helps Good luck!