Honestly, the only way I think a community can grow is by letting it grow slowly. I see no reason why we should focus on making this community bigger, as pretty much every TF2 trader already heard about this community. I don't think Facebook or Youtube will help grow this community. We're hat-trading gamers, not social networkers What I think that we should focus on instead is make the players who aren't regulars in this community, become regulars. And also, rewarding the existing members which were already with this community. Just my 2-cents.
Do a playthrough on youtube with commentary. Extra points if you can be witty and funny during the videos. Hold weekly match and do commentary on them with youtube.
Use Objectors while on other servers, Get people to join by only showing them the objector with the HG logo on Rue's Idea
I know you already have a youtube account but maybe put more stuff up about the server like gameplay or something like that.