I have one from lulu that I love. It's a crossbody bag with two big pockets on the outside that I keep my water bottle and a banana in. A zipper pocket on the back where I keep my jump rope and wrist wraps. Then the main pocket where I keep my clothes.
2 months ago I bought a Longchamp bag for my gym bag. At first I felt a little ridiculous but I LOVE it now, it's perfect! I can fit an outfit, gym shoes, and fleece in there plus keep one cosmetic bag which holds my iPod, ear buds, and a tiny bag for earrings if I forget to take the off. Then I have another cosmetic bag with hair ties, deodorant, etc. I realized that I specifically wanted a bag without organizational pockets to allow me more room in the main compartment.