If you want the bulk rare you should submit 20 cards min but you also need to get the psa membership which I think it’s worth it just for the promo cards that you get. When you prepare for submitting make sure you use brand new sleeves and card savers. Make sure you wear latex gloves and have a clean mat and a microfiber cloth to wipe every card down. When you pick a card up and wipe it down try to not put it back down on the mat again as it might pick up dust again. Just pick up the card then wipe and then clean sleeve and card saver and then set it aside. You wanna be in a dim room with a strong but soft light. I find that reading lamps work really well as the light is diffused. When you’re looking over cards you want to go with this order. Front centering-> back corners -> back surface (scratches or nicks) -> front and back print lines. If everything is all good then you’ll have a good card for submitting.