How many dollars i must have to begin trading ?!
I recommend you to start with a demo account on any exchange . If you put a low ammount such as ($5-10) the exchange will take big fee if you want to withdraw them back
This is good advice. In this case, you may not worry about losing your money and can calmly deal with the nuances of trading. It may turn out this is not what you'd like to do at all.