Actually that amount isn't enough to invest somewhere in bitcoin but if you can study out on how to trade, you can make it higher.
But if you can't, I suggest you to study on how to trade first and on how the market works and moves. And when you are ready for it.
Then buy those alt coins that has a good impact in the market. Because investing that amount in a bankroll casino will not give you decent return either.
$50 is not an respectable amount to invest in casino bankrolls or even in bitcoins the only option left is to invest in altcoins whose value is not too high and wait for price to go higher and if it does then it will be a profitable decision to make and slowly and steadily you can grow your coins.
Surely isn't a sufficient amount if you are going to invest that with bankroll casino's. Though the price of bitcoin now is dropping.
Maybe investing that with bitcoin and just hold it again will be a good place to invest that $50.
Because after the dropping the price will possibly increase again and that $50 can be doubled easily by simply waiting.