This is similar to starting a business, but even better than starting a business. You are allowed to start as small as you want and you can slowly scale up your capital when you deem fit.
Because of greed, your initial capital invested into forex market may be quite significant, but if you happen to lose your capital, you should only deposit $1000 to $2000 for your next try. Of course, it really depends on how much risk capital you have to begin with and allocate a small percentage to start off in forex. Ultimately, you want to be in the game for as long as you can since this is a marathon, pay your tuition fees but hopefully the amount is not dear to you. The goal is to appropriate small amount for learning so you can have huge amount ready when you see results. If there is a point in time that you have to file for bankruptcy or sell your house to be in the game, that is the time you can end your forex career.