There is always doing with anything. Do not risking if you don't feel it is worth it. As long as the website doesn't run or go down you will make a profit and if you don't then that casino is not either unless they are not paying people out to make up for it. If it's a few BTC want to out in for a few months it might be worth it. Just be careful.
It depends since we are talking about Gambling Investments here. It is possible that we could make profits as long as a certain Investment site is running like those HYIPs, but not in the Gambling Investments. Gambling Investments is a 50:50 scale of chance where you could get a profit, it depends on the bank roll that they are making, and the investments in the gambling sites are the one that is using when they don't have enough money to give the winning prices to the players who won.
So, if I were you, I'm going to invest to those gambling sites where do have a high percentage of house edge because, the more the loses of players do have, the more profit you could get, in my opinion.