I will prefer to hold my coins, but I will never invest them in gambling or any other online sites as I am sure that I will loose all my investments in that and will left with nothing in my hands.
And we have to understand that investing it on a gambling site (via playing) or and in any ponzi sites will just gives us a bad output.
So if we want to make our bitcoin grow, go on to those safe methods to considered or if a person really wants a risk then try to learn trading method.
Yeah trading is a good option to grow your coins as it is not pure luck based like gambling, and if you have skills and knowledge then returns are guaranteed.
That's why in the past, I really pushing to those newbies to learn trading. It was sounds boring in the early phase but it was normal since people are still on learning.
If they able to surpass all learnings they need they will able to execute some good trades. Just build experience and eventually they will really have a good returns out of their efforts.