Well, you still haven't told us what discipline you're showing in, so I can't tell you specifically what outfit criteria you should go by. Generally, if you want to upgrade to a fancier show outfit, your first step is to buy a pair of show pants and chaps. I suggest black for both on a budget because it's so easy to switch out tops to match the chaps without having to buy another whole outfit because your gorgeous baby blue chaps match absolutely nothing but the one shirt
. Been there, done that!
After you have these, look around for rail shirts/jackets or slinkies on eBay and equine classified sites. My first year of showing I used a pretty black and silver slinky that cost me around $130 at Hobby Horse, but if you look around and buy secondhand you can find some nice outfits for less.
Don't worry about the blingy belts or spur straps for now, just focus on putting together a pant/chap/jacket outfit.