You can use a credit card/visa debit card to purchase your NFT/s, you will see varied denominations are available for single purchases using a credit/debit card and multiple transactions can be completed. Crypto Currency purchases are unlimited and paid in USDC.
To purchase a NFT using USDC please note, The Karbon Collective uses the Polygon Mainnet Chain with MATIC therefore, you will need USDC on this network and MATIC for gas.