Hi,
I have a standardbred I also show and although I have not found any in hand shows near us, I looked up what to wearYou should wear a hat, tidy black shoes suitable for running (when you trot your horse up), tidy pants or a skirt and a matching jacket. Underneath the jacket you should have a shirt and a matching tie. Your hat should match your suit but can have flowers ect on it. You can carry a show cane for decoration. Your horse should be in an in hand bridle with lead and the lead can have a chain. If I were you, just in case I am worng, I would google it.Good luck for the shows!