I think one hundred dollar is not good amount of money to do trading, but it is better not to do it than to trade with $ 100. I never ask anyone to start with a minimum of $ 100, because when you lose $ 100 you will have a lot of trouble, so I think you have to acquire a good knowledge in order to make trading. Then you can test by investing in a minimum. How do you learn then if you can make a good money for your trading, then you can invest a large amount of money, but the minimum investment is worth $500 dollars is perfect to start trading.