Invest in a casinò (Not dicebitco.in) can be a good choice.
Or, buy an automatic trader, program it and then earn
What do you mean invest in casino? straight gambling?
Some casinos/dices offer the option to invest in house. So you are betting against the gamblers. If the house edge is 1%, the math dictates that you should get a profit eventually (unless someone is lucky and clears all the funds).