Seconded! Old Navy’s workout clothes are really nice and there’s a pretty big variety of styles, so if you don’t want to skew too trendy or too girly or want something a little more covered-up, you’ll still have a lot of options. I got a really nice sports bra there and a few tops that I think are pretty nice (and can also be worn on those gross, super-hot days)

I also occasionally find decent workout-type pants at Costco, so don’t ignore those huge piles of Costco clothes.