If you want to stay cheap for now I wouldnt worry about chaps, a good pair of chaps would take up your whole budget. I would start with the basics and build from there. If you buy things now that will work for you if you ever do get the money then you will already have some of the things you will need. I would start with your shirt, black is a good color to go with because if you do eventually go deeper you can always get a vest to go with whatever colors you decide to go with. I would get a blouse or better yet a slinky shirt. If your going with black, your hat has to be black as well, and a black belt. Black boots. A belt buckle would be a great thing to get to add a bit of silver to your outfit for little cost. And as far as jeans go get a normal blue color, don't get a dark, light or a funny colored wash at all. Wrangler jeans would probably be the best fitted and colored. I would look at some of these sites for things.
Buckles Belt Buckles | Cavender's Boot City Western Belt Buckles
Jeans (wrangler cowboy cut jeans for women are amazing, they have a flat inseem so it doesnt rub on your leg at all) Wrangler | Cowboy CutŪ Original Fit
Look at the Charlotte Slinky Western Pleasure Clothing, Twice as Nice Show Blankets, Hobby Horse, Western Pleasure Show Clothing
Hobby horse basic slinky Western Saddles, English Saddles, Hobby Horse | Copper Creek Tack Shop