Signature campaign is powerful tool but quite expensive.
I think something like referral content with prize 0.5BTC would be better.
But you should take into account only active referrals (with deposite) attracted after starting of content.
There shouldn't need to be any incentive for people getting referrals, other than the fact that they get paid a lot if their referrals deposit a lot (that's kind of how the system works). Hopefully that's enough, it's just getting it out there.
If someone would design a few banner ads that people can post on their own sites, that would probably be most effective so that people have a means to get their name out there.
Yes banners!! Hey if your reading this and can make a few banners... PLEASE do it! The site, the players, and you will all benefit! I tried but the "free" banner sites werent really free lol!