The thing I found most helpful when I was starting out was to read the profiles of some of the other characters. It doesn't really matter which characters... just finding out who is in the world tells you at least as much about what's going on as any specific thread, it seems to me.
Aside from that, a couple of the storylines have plot summaries up, so it might be another good place to start, just to get a basic overview of how a plotline might run. Obviously you won't get the same detail and nuances as if you read all the posts in a storyline from start to finish, but it should give you some idea what sorts of things are happening, especially when things are complicated.
http://www.tharshaddin.com/rp/viewtopic.php?f=2&t=1139 (This is a nice summary Julen did of the Lightsword Saga-- which my character is involved in. Not trying to toot our own horn or anything, just it's a pretty complex story and it can be helpful to have an overview.)
http://www.tharshaddin.com/rp/viewtopic.php?f=2&t=1146 (Another summary by Drake. There hasn't been anything posted in this storyline for awhile, and it seems to be either done or on hiatus.)
The other thing I would suggest is reading some of the currently active threads. Not because they're somehow better than the older ones obviously, but just to give you an idea what's going on in the world right now.
That's about all the advice I have. Once again, welcome to the board.
