Well, there is no required amount. In my opinion best way is to start with the amount of you are willing to lose.
That is not enough, your capital needs to be big enough so you're not wasting your time when you are trading, I say this because a lot of people have a capital so small that they need to make very big trades compared to the size of their holdings they have and it doesn't matter how good you are, if you do this you are going to lose your money very fast.