For gambling casino , I will recommend to start advertisement here on bitcointalk. The best way is to start the long term signature campaign.
It might be more appropriate to promote precisely that many gambling activities from high traffic sites but only few active gamblers, I think this forum is very appropriate to promote gambling as many active gamblers and gambling campaigns are very popular in this forum.
you're right on this, many casinos prefer to advertise their site on a reputable forum like this of no doubts, one thing many missed out is when considering the cost for their awareness campaign, it wreck down their motivational spirit towards pushing further but forgetting that it will do them of good than not, while many sees this a privilege to advertise some don't, but advertisement goes an extra miles beyond the ordinary reach of the casinos in making an awareness campaign and this is one of the major reasons why some have made it on high reputation because their casinos is well known everywhere.