I agree with you. Besides using social marketing and forums, you could also use adwords. Of course it will need some cash to start, but it will reach targetted viewers and possibly the buyers too.
I think before you jump into your traffic generation strategy for your gaming blog, you need to have a revenue generation strategy. That will in some instances drive how you go about looking for traffic. I too run a gaming blog. Initially I was trying to monetize the site using advertisements (adsense and others) but I realised the volume of traffic required for that to be a lucrative income stream would be astronomical. So I found some other ways to monetize the blog and because some of those are high value, I can get away with some PPC ads, small targeted media buys and CPV traffic from things like TrafficVance. Be careful with gaming blogs, they can very quickly become "Build it and they will come" type things and the people never show up.
I would say it really depends on your goal. If you need new players, then may be it is worth spending some money and purchasing relevant advertising, also you should yourself spend time at game sites and attract users. If you just need traffic (quality does not matter) then you can submit your site to directories, use signatures, leave multiple comments - this will help to get initial traffic to the site.
New content is updated daily, per day can be a forum to learn about knowlege that you can do well it.
Why don’t you sell ad places at your forum. That would be best for you’re your forum. You can generate income as well.
I once had a very popular gaming blog - never earned much. I would suggest going with other verticles.