J.B.
I get tops at Target - they have a decent selection of bras as well as tanks and tees. I am way more comfortable working out in a real exercise top instead of a regular t-shirt - they breathe better, fit better, stay in place etc.
For bottoms, I am heavy and hate having shorts ride up so I really like knee-length shorts that are fairly fitted. Nike Dri-Fit are my favorites and I have a Reebok pair that I also like as well. They are really flattering, comfortable, don't ride up and I don't feel like if I move in the wrong direction someone is getting an eyeful of my upper thigh LOL. Those are expensive though (maybe $45-$55 a pair). You can probably get something similar in Target that's on the long side. If you're doing strength training you'll be on the floor and want to be comfortable.