In my opinion, it is impossible to say a specific amount that will provide a stable daily earnings. It all depends on the situation and the specific situation.
Exactly you have point, it all depends on how much you are willingly to take risks in crypto. In day trading you are knowledgeable first to avoid lose. You have time to observe the swing price of coins since you will do day trading. Invest only on how much you can afford in trading.
do only a few coins that have the potential and enough capital, because if you only trade daily without doing further research it is a waste of time and does not provide profit.