Whatever you do, do NOT spam forums. It is a very fast way to fall out of favor.
When you use a forum, take part in the conversations in a way that helps others too. Forums are communities and a give and take. People know and respect each other and help out as they can.
There is no turnkey solution to successfully advertise a gambling site. If there was, none of us would be in business.
It’s a learning process, you want to learn about SEO.
Learn about what sort of site appeals to the specific demographics you are trying to address (if you are a young male and want to address older women who play slots, for instance, they may not share your taste in site layout. Learn what they like.
A good place to start gathering information is here: http://www.casinoaffiliateprograms.com/learningcenter/
Read as many posts as you can and ask deeper questions when you are trying to nderstand something. There is no shortcut.
Good luck!