Also, always ask yourself this: what does my website offer that people can't easily get in other places? Your forums seem to have general forums, RMXP forums, forums about your games, and forums about others' games.
- General forums are everywhere. No one really joins a site because of those, they're just extras for the members that visit primarily for other reasons.
- RMXP forums are... well, they are everywhere too. And unfortunately it's pretty difficult to get an RMXP forum off the ground since there are already several large ones that get the majority of the traffic.
- Forums about your games are good. But it's only going to draw in traffic if people have an interest in your game. If this is your focus, you need to get your games out there more and pique people's interest, so if they want to know more they can visit your site.
- Others' games... that's good, I guess, but something tells me if I want to visit a forum for a game (especially an RMXP game), I would go to the creator's site first, if not, I would go to one of those big RMXP sites I mentioned previously... so sites like yours would be third on the list as far as that goes.
So really it seems like the best thing you're offering at the moment is forums about your own games... but if people haven't heard of them they have no reason to join! You need to get your game out there a bit more, and the best way to do that isn't really advertising in my opinion; if you make your game great, it will advertise itself. So that's where I would start if I were you.