I've always had problems with girl's clothes fitting (I'm FTM), but I never had the courage to shop in the boy's section. And every time I get the courage, I have to leave or something. My parents allow me to buy boy's clothes if I want; they don't really care as long as it's appropriate (not showing stomach or underwear or something), I'll wear it, and it doesn't cost too much.
I agree with thrift store shopping; I've grown up with this habit because I'm not rich, but really, you can find nice stuff in there, and it costs only about $3.00 for a shirt. My sister's found lots of name brand jackets & such which would normally go for around $100. Another good thing about thrift stores is that even though there are sections (men's women's), they aren't always as clearly marked, and each item isn't marked either, so if you aren't allowed to buy boy's (for FTM) or girl's (for MTF) clothes, you can easily get away with it.
Also, I agree that Ross is good; not too expensive and has some OK stuff. It's kinda hard to shop because of all the messed up sizes. You'll just have to learn to use your eyes and a few techniques to find something that might fit. But there is a more likely chance you will find something that fits because of the messed up sizes.
A tip (some of you may already know this):To see if a pair of jeans might fit, hold it tightly to your waist. If the side seams of the jeans meet the side seems of the jeans you're wearing, they should fit. And if all else fails, buy a belt.
