Alright here's what I think, don't take anything personally just trying to help you out
When starting a forum, you always just condense the forums. To many categories isn't needed and makes the forum look extremely inactive. Another thing is, before you open make sure to add content. Go to each forum making posts by yourself or with a staff member. If needed, create a couple of fake accounts to spark activity.
The niche you chosen is a tough one. There are tons of gaming forums out there. I'm glad your domain doesn't include a generic title, like GAMERZFFORUM or something of that nature, so good job on that. Maybe customize your theme so it is more gamer-like... that should help!
Hope that helps you. Good luck!