I'm currently having a problem building a wardrobe, too. It is really frustrating because no mens clothes fit me and the boys clothes are so short its not even funny. Plus, clothes are just expensive in general, even at thrift stores. I love thrift stores and its always fun to find outfits (shhh I like shopping sometimes...) but you can't get a good shirt for less than $8 anymore and they are used! I can get new ones at walmart for the same price. It is usually such a hit or miss lately at thriftstores I don't even bother anymore. Half the time even if I do find something I like that I can afford I don't get it because it has a weird 'vibe' to it.
You can try craigslist, at least in my area, people are always offering free clothing. Most of the time it's women's or childrens.
I also recently discovered this site called Aliexpress and they sell super cheap clothing. I just ordered two binders, leg warmers, gloves, and two shirts for about $25 (free shipping from all the sellers). I made sure to see the seller and item ratings before I placed an order and if it goes well I'll get some more stuff because I have literally been wearing the same two pants and two shirts for months :I