Thanks for the tips, all. I'm really not all that preoccupied about gaining weight, I just think it'd be good to have a bit more muscle mass in general, as my legs feel fairly weak--power-wise, not endurance-wise. I don't think I'm going to be shoveling as much protein down as I can; I once did that for a year, gained about 7 lbs over that period, pretty much devoting myself to working out at the gym. Unfortunately, I can't afford a gym here in NY (the rates are ridiculously expensive), but I'm going to look into purchasing some weights.
Thanks again for the tips.