Clans are for CB, pretty much exclusively. As a new player, you won't be able to get into a good CB clan, but try to get into an active clan that is at least progressing in CB. I was lucky enough to get into a clan that had cleared easy & was working on normal (which we have since beaten).
Obviously long run you'll want better than that - I've kind of outgrown my clan, as it doesn't look like we're beating hard any time soon and I do by far the most damage on CB. If you're REALLY lucky you'll join a clan that continues to progress & that you can grow with, though honestly in all likelihood you'll leave your first clan at some point. (I haven't yet, just haven't been motivated to look for a new one, and only recently have I gotten to the point where I feel I'll be able to contribute on brutal).