You know, 50 bucks is so small investment at that moment, but those who invested 50 bucks in bitcoin in 2009-2010 are rich people now. Would be to, i suppose. But it took almost 10 years, and we dont know the future price of bitcoin in 2019-2020.
So I recommend to spend this amount on such things that nobody dont know about. Maybe buy some mooncoin (MOON) - development started in 2013 and now it is continuing rapidly. You can buy it for 1 satoshi per coin now. It seems to me that moon is going back in game very very soon.
Another suggestion - eltcoin (ELT). New project instead. If you buy it before 31 december you can stack it in wallet and gain generous airdrop.
And another one - BitcoinWhite(BTW). The project is only on ICO stage, but you can participate in twitter bounty, it is very simple. And it already has working blockchain(its own), delegates system, and other features.
So the amount of money you want to invest is not so important as the correct choice of direction this investment sent to. I just gave a suggestion, now its time for you to make your own research - dont believe my words, check it yourself

100% this^

The best coin I know of that fits this bill is Spectrecoin.

I would choose 2 or 4 projects, and bought a small amount of coins. Depending on how they behave in the market, I would change priorities in the ratio of coins.

the amount of 50 $ was very little. I think it would be difficult to get a big enough profit. but you dont have to worry, lots of cheap altcoin. you just need to research and learn every altcoin.
buy and hold for 2-5 years to come.

The recommendation are limitless but they are no quarantee for success. U might lose ur money but my recommendation is to look for coins below $1 with high liquidity which just dumped and invest in about 3 or 4 wait for dem to pump.or u can just buy cardano,verge,nem and ripple and keep dem for a year or half

A very risky move can be done, like trying to put it in gambling first. But a wise decision would be, try to find a good ico and use that amount to buy a good quality coins that has a good tendency to increase its value, then I'll hodl it.

50$ is not enough to invest in good coins but still you have some choices to invest in, you can check RDD, Dogecoin and XVG. These can be prove worthy coins in long term.

It is a very difficult selection because 50$ is too low for investment. I could leave it at Bitcoin and expect to be valued or invested in Waves.

I would invest in trading or in ico. The etherium grows in relation to bitcoin. You can buy it.

Invest in a good ICO or recent post-ICO with a team that looks fantastic to you. That's my advice.