What material clothes should I wear to run?

Especially in the summer wicking fabrics are the answer if running outside. Cotton is fine, but it holds your sweat and gets heavier as you go. You'll be amazed at how much more you'll enjoy a run if you wear wicking fabrics. I bought my first outfit at a Walmart and for a low-cost option it wasn't bad. Until your shopping trip try to run in more polyester fabrics, espcially if its really hot outside. I would say this matters more for the shirt you choose than the shorts, you can get away with what you're wearing for shorts until your shopping trip.