I buy mine from the clearance rack at Meijers (which is similar to Walmart). I just bought a pair of capris (they went up to 3x or 4x I believe) for like $4 and a sports bra tank top thing for like $8.
Or Old Navy. They sometimes have cute and cheap work out clothing there too. If you can wear xxl or 20, I think they still sell those sizes in store, but the plus size stuff is only online now.
I have some of the most mismatched workout clothes. I have a few pairs of yoga pants from Old Navy that I love, a few pairs of fleece pants, one from Walmart, two from Old Navy, then I have a few pairs of shorts that I bought at Walmart a few years ago. None of them were actual exercise clothes, some where pajamas, the shorts were just with the normal plus sized clothes a few summers ago. Sometimes I just go with mens activewear, I usually can find it in larger sizes more easily than I can find women's.
I get my yoga pants from Cato's and the rest from Target...although I did pick up some awesome Danskin tanks w/built in bra at Walmart on their clearance rack (funny cause I've never seen them before there!)
Try Kohl's. I've had luck with Walmart, but you have to catch them right when they stock as they sell out quickly. I have no luck at Old Navy as ours doesn't sell Plus sizes anymore.
Stitches 2 for 30 dollars, but yes wal-mart or giant tiger is my best place.
I was skeptical about buying about yoga pants, and regular jog pants would do just fine, but i absolutely love my yoga pants, even when im not working out
before now, I just bought comfy stretchy pants and t's at fashion bug, but now that I can fit into a 2x, I found lots of good stuff at target. They only go up to a 2x in the workout clothes though