To make your cat comfortable you may want to include a shelf, bed, and his favorite toy. Your show cage will need a food and water bowl and a litter pan. Usually the show will have litter and food available. But is always wise to check. If your pet is finicky on what he eats it is better to bring his favorite food.
Combs work great for longhairs and a chamois for shorthairs.
Claw clippers are essential for keeping your cat's nails clipped. All shows demand that the claws are clipped, and the judges appreciate not having a frightened cat with long claws. Remember to do front and back. You may want to bring paper bags to dispose of your garbage. Don't forget a pen to mark your catalog with.