I can easily turn $5 into $10; buy candy bars and sell them to my neighbors next time I watch a sports game in person.
So I'm really confident I could double $5. But could I double $50? I'll definitely get caught trying to sell $500 worth. So I just sell a little more all the time while remaining cash flow positive, and that's how I learn the limits of the market without going bust.
If you know how to turn $1 into $2 (of value) you should be spending as much money as you can.