I feel that in your case the first step is not about finding a broker, but trying to realise what trading is all about before yu deposit the money. I strongly recommend you to browse through such trading forums as this one in order to get some basic picture of trading.
In a nutshell, trading is definetely not an easy source of money. You should understand that you need to work really hard before you'll get some decent profit. More than that, make sure that you have enough money for that. Surely, you can start with $100 but trading with such small sum of money will never bring you any tangible results which will motivate you to improve your trading and your knowledge about this activity.
If you decide that trading is a suitable activity for you, then you have to choose a broker. During this process you'd better pay attention to the official regulations and history of operations. Beware of scams, there are still lots of fake brokers which will disappear within a week taking your money away.