Just looking at the most recent posts in the Covens section, it appears that Practical Witches, Teen Witches, The Air Element, and Element Magic may all be open to new members.
As for more people being active, I think joining a coven may be a good idea. the open chatter is often either quiet, or silent, or the topic changes quite often (it happens to be lively at the moment, however). But I've heard that coven chats tend to be much more lively.
I'm in Practical Witches, and they are open to new members. In fact, they are rebuilding. If you want to apply, pixa and Agiel are the High Priestess and High Priest (respectively) to contact and apply. I would check out each coven's page, and then find the one that suits you best. Then, you would message the High Priest and High Priestess with your application. It will take a few days for them to get back, as they have to look over the application and talk to each other about it.