At least a month or so. I would invest in an established casino that's been around for a long time and put your money in for at least a couple of months before you consider withdrawal.
We does have a limited option when it comes to casino investments and if you consider the risk factor then i would stay away from it as i would rather gamble and multiply my asset than investing in a casino,because i am having a good time with sports bet for the entire month and winning a good amount with minimal loss and so i am confident to say this at this point in time,it might differ later. 
In gambling, there is no guaranty that you will have the same good time in future as well. Because it all depends on luck, so I don't think it is a good thing to gamble on growing money instead of investing. I will invest money to grow and will gamble only to get some fun during my free time. Also, sometimes it may need more that a couple of months to show good profits in casino investments.