You really cant expect to make money on free domains either.It cost 10 dollars to register a domain ,it does not even have to be a gambling related domain and serps can pick it up but i am sure there are lots of gambling domains still out there. I bought an existing website that was loaded with free money stuff and all key words were free money stuff.I am gradually replacing the free money stuff with 100% bonus or better offers.I can see the difference already .There are some free money sites that still convert but it takes a month or 2 sometimes before they will deposit.
Forums provide alot of traffic ,one of mine gets me 200 hits per day which is 6000 per month in uniques and i am lucky to get 12 deposits a month on that traffic.