Facebook groups. It is fairly easy to join a group with over 2000 members, just find a group that relates.
1. Open Facebook (or sign up)
2. Below your banner on your main (ego page) there is a menu (Timeline - About - Friends - Photos - More)
3. Click More and scroll down to "groups"
This shows what groups you might be interested in joining or already joined. You can create a group but then you need people to join.
Also
Search "Unity Games" at the top, then choose Groups
Here is what I found right at the top
Unity 3D Game Developers at 35,426 members. This is a closed group, that means you have to join to read and write posts. Public groups means you need to join to post but you can read all the posting. Secret Groups can't even be seen and are invite only.
I would also suggest you join some gamer groups, people looking for new games to play.