Go to your nearest Good Will store. For under $5.00, you can find some nice jackets and shirts or tops.
After you have made your selection, you could do a little customizing with iron on embroidery strips, or now they even have iron on "bling". For a very small amount, you could have your own one of a kind design and show outfit! I personally think this is the way to go for show jackets and etc., because if you're like everyone else I know, they end up globbed up with baby oil, hoof black, and anything else your horse can rub on you. When you've paid such a small outfit for a jacket, you don't feel nearly as bad!