you can grow your bitcoins through a multiple of ways, you can grow your bitcoins if you invest your money in gambling, you can also grow your bitcoin if you invest your money in alt coins, you can also grow your bitcoin if you lend your bitcoins to some one.
Maybe it is not a good idea to lend your bitcoins to someone. Your idea of investing your bitcoin in gambling, by putting your money on the house. You know it will grow because the house always win in gambling. YOu just have to pick a good gambling house, the one with a lot of gamblers going in.
I see that idea as well an effective one, by putting you money in the gambling sites bankroll you are ensured of the winnings because the house always wins and that apparent to us. Instead of just holding it in our wallet why not put some in gambling sites for double impact on growth.