As in "Pleasure Show" or a pleasure driving class at an open show?
I adore those Victorian clothes! However, at driving shows, costuming is looked down upon. Everything needs to be conservative. Go to the Goodwill, and look at jackets. Then you can buy several. Make sure the sleeves are long, so they cover the top of your gloves. That makes your arm, hand and rein one continuous line that looks good.
For your hat, since your donkey and cart are small, I would stay small. I find a lot of hats in antique shops, especially in small towns. It can have feathers and ribbons on it. Check out hatsbyKatie.com , and google Sherry Lower for her shop name, I cannot think of it right now. Both will have AWESOME ideas.
Lilly, I am SO sorry! I thought you were Littrella! Everything above applies, except the donkey part!!