$USDC
Currently, BTC/USDC is trading around $84,318 per BTC. Since USDC is pegged to $1, this means you’d need 84,318 USDC to buy one Bitcoin.
If you’re looking for small trades, you can buy fractions of BTC with as little as 10 or 50 USDC, depending on the exchange you're using. Most platforms allow you to trade in amounts as low as 0.0001 BTC (~8.43 USDC at the current price).