Lauren, I've been practicing for a while; I use to wear cute clothes. Now, I don't care. At class, I have a male teacher and a lot of men in the class, so I try not to wear anything low cut. Usually, a not too big t-shirt and I tuck it in. Sometimes sweat pants and sometimes yoga pants. I take a hand towel with me. At home, if what I'm already wearing is comfy, I don't change. Home practices is gentle, Kripalu style yoga.
Bill, Here in IN I've only seen my teacher take his shirt off. All the other guys wear tighter fitting tees or tanks and gym type shorts. But if you don't want to wear a top, then don't. I can't imagine anyone caring.