Definitely don't worry about your horse's color! It's probably even a benefit! The judge will see -Rider on horse with cool color- instead of -Rider #123 on another Chestnut horse-
As for your tack not costing a fortune...it's not all that big of a deal. As mentioned, if it's clean, well-fitted, and appropriate, it's good! Good grooming and turnout helps more than a $2000 saddle. I'd just be sure to avoid super-outdated trends...like rust colored breeches for English.
I bet while you're in the arena at your first show, there will be some little girl on the sidelines admiring you!
And boy, you sure have struck my curiosity! What color is your horse??