I can assure you that SEVERAL of us here have gone to shows not having the fanciest horse or most expensive tack! Go anyways, make yourself as presentable as possible, and have fun! From the back of a galloping horse people won't be able to see what brand of saddle you have! Make sure your tack is neat, conservative, and clean and that everything fits well. Bathe your horse, pull his mane (it is amazing how much of a difference a well kept mane will make!), and be proud of his color! People these days are really into unique colors and you'd be surprised at how many compliments you may get. (what is he?) I'm pretty certain I have the only red dun pony in the entire hunter circuit in my region and people LOVE him!
Last year my friend and I thought it'd be fun to 'crash' some dressage shows with our hunters, our brown tack, snaffle bits, and simple nosebands. I was riding the only buckskin pony (competing against fancy WB) and yes people stared, but you know what? We won almost every class! And people this year are like, Oh, I remember you! You're the one with the cute pony! Plus, we had a TON of fun! Just go and have a blast without worrying about what people say or what ribbons you get. Esp since it'll be your horse's first show! GOod luck!