I have $3000 USD to invest, is it worth it?
What sort of returns should I expect
Bitcoin casinos and casinos in general are always expected to make a profit since the chances are in their favor ie the house edge. So investing in a casino will profit you in a long term. The return percent depends on how many users use that casino and the total wagered amount. But beware only invest in casino that are trust worthy because they can scam your money anytime.
There is no guarantee to that and to all of course, the hiuse can simply tell you they lose huge amount of capital including yours and you may never get responce when you ask for records. If you are into gambling already, you might as well just create your own casino. There is a crypto that will allow you to create.