If doing it full time, starting from let's say $10,000 to play with, and btc being in between the same volatility now and how it was about a year ago when it was at around 6k..what could you net a month, realistically?
Candidly speaking there is no fixed or even rough figure as of how much one can earn with a given amount for trading because it all depends on what decisions you take like which coins you trade and if you are only trading Bitcoins lets say and price trading is the only option then there are still number of factors like what is your risk appetite and how much you are willing to use into each trade.
You cannot buy bitcoins with all the 10k you have for trading because if you do that, you might have to wait months in case the price drops and hence a number of factors will decide how much you can earn. The best strategy one can implement though is just buy and hold the coins because its been years and that seem like the easiest yet most effective strategy.