If you mean what is the smallest you can buy-in for and hope to build, I guess $10 is okay. Ideally, you would play freerolls
and small Sngs to build that up. If you prefer cash games, then you should start with at least $25 to have a chance to ride out some of the waves (variance can be a beast). Check out some of the twitch/poker school videos on playing micros if you are going to go the cash games route. There are a lot of good players with good strategy tips out there.