There is nothing wrong with the signature campaign, but of course it is not enough to attract new gamblers in this forum. FlushCasino, you could offer special promotions on the bitcointalk forum like other casinos do.
That makes the system interesting for gambling newcomers, and for experienced gamblers as well.

You may consider creating some promotions and contests exclusively for bitcointalk forum and promising some special hot offers to the members here. It is better than simply trying to drive the site traffic, because you have to get some committed gamblers here.