The biggest community appears to be realm nonladder. Everyone plays ladder to get ladder only stuff and then adds it to their collection when the season ends. There are a ton of nonladder games on realms. But ladder is still going strong too. Welcome!
Which makes playing ladder a little nicer, less annoying people ;-)
Also, (in the beginning at least), you won't feel left behind when you start from scratch!
Ps: feel free to add me *redflux, I've also made a thread in the player-matchup-forum here, if you're looking for a good time just playing, or want a quick boost/items to catch up a little (I don't have godly items, but I'm friendly and helpfull )