'If it's possible to send money from card to another card, then it is absolutely possible to buy crypto.' <- it would be impossible to buy anything in that scenario. You can switch to cash but you will be limited in safety (or keeping the money safe) and online transfers. And games will be least of your worries/interests.
'It's called P2P on most platforms.' <- Peer to Peer (P2P) for short is a method where you buy or sell the item (in this case a cryptocurrency) from another person without mid-parties. In those sites you contact a seller, if is available start a chat with him/her, pay via bank transfer/paypal/face to face with cash/etc, send the proof of payment and the other part transfers the coins to your wallet.