what will you do with that 15$ once you sell it? go to Mc dolands and buy yourself two menus? cause that's what your return is worth now. If you want to invest in something it's better to invest more money than to invest little, because in order to go through this whole process, you are wasting some energy and though into it (how to buy Ethereum, when to buy, when to sell etc.) all this takes time and energy. With your 15$ return you basically value your time and energy at 15$, which is not a lot. If you want to make your time worthwhile and make some serious invesments, then you should risk gaining and losing more. ETH will rise more in the future, but considering your low stack (50$ invested) I would go and invest it in somewhere else, maybe an ICO were your potential return is much bigger.