If you want to grow your coins, start a lending service.
Only lend money to trusted users, or people with valid collateral that is worth 120% of the loan amount & make sure it's held by escrow. If you decide to gamble, I recommend exchanging BTC to CLAM & gambling at just-dice.com. Very good site & I made a lot of profit ($50) from $4 that I eventually lost lol
There are two problems in there,
1, it is very slow earning for today world, as now business like that cannot give a luxurious life for the life nowadays,
2, It is a risky business, sometime a person is unable to repay and selling collateral sometimes become very hard, so wasting of time and investment. Try to start an offline business.