For me having an small investment still make sense, especially in gambling. We all know gambling is very risky to play, so the better thing that we can do for us to not lose a lot of money is to just use small amounts and not to bet in high bet so that we will not regret if we lose it all.
It does make sense but if you'll invest that small amount in gambling, chances of growing it is very little. Not unless you are talking about the investment in gambling as the one you are going to gamble with your bitcoin. I don't think it's going to be a big deal. As the only way to invest in gambling is to deposit your bitcoin to the bankroll of that casino and not by gambling it alone.