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.