I have a steam group for Dirty Bomb called C-Cor. We have occasional giveaways of case keys, steam games, and the like. The group is for players who want to get together (of all levels) and join in casual or competitive matches with others from the group. There are forums on the steam group, and also a teamspeak. Very beginner friendly, but also good for players who like to engage in competitive matches.
There are no trolls/scammers/annoying little kids in the group, so no need to worry about that (they will get booted immediately).
P.S. It is a very new group, so we still need people to get the word out (i.e. people who can stream our competitive matches to twitch/youtube/etc.)
Look us up on Steam, click the link above, or send me a friend request on Steam to join.