Any polyester or poly blend that is mostly poly should be relatively wrinkle free, Diana. Plus they come in such pretty prints. When you're in the fabric shop looking for fabrics, scrunch a corner of a fabric that interests you in a small ball in your hand and release. You will see its wrinkle factor right there. I've passed on many a fabric that failed that wrinkle factor test.
I make at least one circle skirt each summer, and love them. I like using linens, silks, and rayons, but I don't see why 100% poly wouldn't work--by that I mean it shouldn't be too hot, since the skirt is swishy. Plus it would be wash and wear.