I ride english jumpers. When I school I wear a polo tucked into my tan breeches with a belt and tall boots or half chaps. When showing I wear a white show shirt tucked into fancy breeches with a belt and newer tall bots. Over that I wear a black or navy show coat.
Depends on what discipline. When I'm riding English, I'm always in breeches and my tall boots with a tee or tank in the summer or sweater in the winter.
When I used to ride Western, jeans and boots with tees, tanks, or sweaters. Plus my ultimate accessory: my helmet!