what do you expect 50 USD return to you? the easiest way is to buy btc and hold for a long term, if you want to earn huge profits, then you must do your own research and take a high risk
https://www.google.co.uk/search?q=bitcoin+earliest+price&ie=utf-8&oe=utf-8&client=firefox-b&gfe_rd=cr&dcr=0&ei=V4S6WefkBayk8wfI1JWQCA
I hear $1 buys you over 1000 bitcoins in 2009
now we have $50x1000=50,000 BTC
50000x$3500=£175,000,000=$175million
so $50 gives you only 175 million dollars
it is not that much to be honest
