You could actually make money trading with that capital. Before you dip in though, look and observe how the coins move in the index. Research coins you like, if they have developments or not. Then, once youre comfortable, buy into the coin that you like and know will have good development. At this stage, you can opt to be a day trader, buying and selling on the same day, taking advantage of market volatility. Or you can become a bagholder, you buy a coin, hold it for a long position, then cash out when their coin goes through the roof.
Pretty much well said, you can also join the ICO campaign with early participant bonuse, some ICO gives upto 50% bonus, so by calculation that 100 usd worth of btc might be 150 worth of BTC after the ICO because of the bonus given to the early participant. You might get lucky like those who participated in ethereum if the price of the ICO you participated increase in price value.