I was lucky enough to get online a few hours after the event started, so I kinda know what's going on, and I'm slightly in all three of'em. Basically, I skimmed'em so you wouldn't have to.
Don't try 3, it's way complicated. 1 isn't bad - just read all the posts from King Oa and Young Akala (there are like seven posts) and you'll know what's going on. The easiest one to join, no reading required except for the first post, is absolutely number 2. Everyone's just in the two parties, celebrating the end of a war that they can't quite remember. Things are about to happen, things I don't know, but if you pick one of the two groups in thread 2 and write yourself in there, you can still get in at the ground floor, believe it or not.