Welcome to SARP, Scarlet!
One thing to know, whatever your particular tastes in RP and sci-fi flavor are, it's quite likely that there is a niche for you somewhere around here. Just as a quick crash course of the major factions, you have the Yamatai Star Empire, which is heavily influenced by Japanese pop culture and anime with a little sprinkling of old Norse, then you have the Democratic Imperium of Nepleslia, which is predominately populated by cloned super-soldiers with a heavy 1980s action-movie-star overtone. Other big factions include the Elysians (giant winged Angel-Amazons), the Hidden Sun Clan (bipedal feline warrior race), and the Neshaten (fox-people). This is by no means an exhaustive list, of course; there are a lot of them out there.
There are also a number of smaller factions and RP threads out there, so don't feel compelled to join a big faction if you really don't want to. Getting involved in one of the big factions is usually a good way to acclimate yourself to the setting, and after you've cut your teeth you can take that character somewhere else, or make a new one. As an alternative, there is the Open Roleplaying forum, where prior approval for your character is not required. It's considered good form to ask before joining someone else's RP thread, but most people will be willing to accept you. You can also make your own and try to attract other players. The only kicker with the Open RP thread is that it's considered "quasi-canon," so depending on the nature of each specific RP, it may or may not be considered to have actually "happened" within the SARPiverse as a whole.
If no faction appeals to you at all, there are a number of independent plots to consider as well. I run one called The Fringe, which is currently at capacity, but there is always the possibility of losing a player, and I am open to "guest starring" roles as well.
Hop onto the IRC if you have any questions, or feel free to ask anything about which you need clarification on this thread. Again, welcome, and happy RPing!