I CFJ: It costs 2 hooves to get a jersey for a horse and add a horse to that horse's pull.
Evidence: R2672 states in relevant part "Each player CAN take one of the following actions (weekly race actions) if e has not already taken one this week...* get a jersey for a specified horse by paying 1 hoof, also specifying a horse which is thereby added to that horse's pull by paying 1 hoof." Clearly in my view you have to pay 1 hoof to add a horse and 1 hoof to get a jersey, as the fee appears twice. But you have to take the action all together because this all appears under one dot point, which is intended to be one action (for the purposes of the horse rule). So you have to pay 2 hooves total.