H&M has a decent sportswear line. I love their yoga pants, though more often than not they tend to be pajamas. I inched into buying proper running clothes because, surely this was only a phase, and my first gear came from Target. Now I subscribe to Fabletics and have both a summer and a winter running wardrobe (I’ve been 80% happy with Fabletics but I don’t recommend them to someone just feeling their way into gym clothes). Nothing wrong with Target. I’m just lazy and like my clothes to come to me.
Don’t let the whole gym-body thing stop you from getting decent clothes. A lot of the pricey stuff is a rip-off, but it can make a major difference if you have a shirt that doesn’t billow or ride up while you’re getting into poses. Also having something in a nice color can really boost your mood.