Let them come to you. The people who post a lot and want a clan are the ones that apply. How would anyone get good members if that would not be the case? ;) Or you could invite people (Not recommended for you yet.) It would be better if you were still a bit more new. You could recruit a average skilled guy in-game, tell him about your forum, and make him post. Tell him the standards are high (even if they aren't) to be in your clan. They'll try harder to exceed your expectations, and Wha-la, active member! Take them at max 2 though. 1 would be hard enough. (From experience)
I just used 5 as an example. Really though, five isn't too much >.> Lol Just set a standard. If they abide, they become active. Exercise your clan! ;)