50 $ are few .... even if you invest in the right coin you will earn little .. I would invest in projects that are worth very little and that can potentially make 100X ... read on coinmarket ... there are many coins and choose the one that you inspire more.

Something like Sexcoin (SXC). $50 would get you around 250 SXC. We've seen what happens when a coin takes off so if SXC becomes popular in the adult industry, possible, you would be looking at a valuation of something like $5 per token which would be a nice ROI for that $50 investment.

another job

I see everybody noticed it is a very small amount, but nobody asked how fast and how much you would like to multiply it. So if you are not in a hurry, I'd say it's pretty obvious that Bitcoin or ETH or Einsteinium are some good options to multiply your money... and start again, with a larger amount of money, once you've reached, say, 500 $.

i would invest the half to the bitcoin or ethereum and the rest was to invest it on the multiple altcoin because on altcoin you can accumulate profits in a short period on time so while you are busy at short term one the long term is still running

1:Ripple
2:cardanno
3:Verge
4:stellar
5:siacoin
6:golem
7:Basic Attention Token

It is a little sum of money. I would buy some cheap ones such as oxy or others because I can buy more and have great chance for them to rise so I can make more money with it.

find coins that cost cents, look at the prospect and buy them 

I will it in topia or coinexchange will find 2 or 3 coin that have potential, good project to pump and buy.