you can grow your bitcoins through multiple ways, if you invest your bitcoin in gambling there you can really grown your bitcoin in a very very fast mood.
I don't think investing gambling would give us fast profit, I have invested on it so I would no. The profit that you can get in gambling is just a certain percentage of your total investment, that is because you are only putting on the share of the total money pot.
I agree with your opinion, the best way for growing up bitcoin in my experience is trading bitcoin or altcoins, although it will become hard for me to profit consistently from trading. Gambling is just for if i have got profit from trading and never making it becoming active income.
Trading is not a gambling but you have to gamble with it, it needs money to make money and it it is not that easy as like people are expecting it is. For you to make money in trading you should have the right knowledge alongside with a good experience.