Before starting any signature campaign, first try to develop a professional ANN thread and try to convince people play at your casino. ou can start my giving special offers / bonus to people who join through bitcointalk. Once you see people joining in, then you can start a signature campaign etc.

Also i hope that your new casino site is unique, attractive with things like no kyc,  easy registrations and low withdrawal fee, etc so that people don't have any objection to playing at your site.