Won't work for credit/debit cards, can't extract the encryption keys needed to confirm transactions from the original card. You can try it without the ring, just use the flipper to try and emulate the bank card and use the flipper as if it was your card. Won't work.
To get a bank card ring you could open up the card, take the electronics inside, and diy a ring with it inside. I'm sure someone out there has done it