So this will be my first con and also my first opportunity to participate in Society games. The only books I have are the CRB and RotR. I'll probably bring them both for getting them autographed, but do you guys feel I should buy any other books as prep for coming?
Also, is there any other kind of prep I should undertake right now to participate in the PFS games or can I arrive and register, draw up a character and participate directly?
What other game-related materials is one advised to bring?
I'd recommend making a character before you get there. Make sure to download the Guide to PFS (version 5.0), and look at the chapter about making characters. Stick with things from the CRB, since that's the only book you have, and you'll be good.
If you're going to be playing in more than one game, make two or three characters, so you have a backup in case something unfortunate (and deadly) happens....
Last year, it seemed that everybody had a figure (or, sometimes, for instance in my case, a stand-up pawn) for their character. I'm not sure what would happen if you showed up without one; I suspect the GM would be able to provide you with something to use.
I'd agree about making a character or three before you go, just because it's fun to play something you've dreamed up and created. But they'll have plenty of pregenerated characters on hand of various levels, so you could show up with nothing but an interest in the game and be fine. In case you're not familiar with it, the Guide mentioned above by rknop is the Guide to Pathfinder Society Organized Play and it can be found on this page.
Last year I didn't bring any minis, and I will try to bring some this year. That said, you can always just use dice to represent characters on the map, and your goodie back when you arrive at registration should include some minis as well.
Bring a pencil! Dice are good too. Have fun! See you there.
Any material (feats, classes, traits, spells, prestige classes, or equipment) you use for your character(s) must come from a book you own--either in physical form or in legal PDF purchased from Paizo.com. And you're technically required to have any of those products on hand when you play that character to prove that you own that product if a GM asks. Printouts of the appropriate pages from the PDF that show the watermark with your paizo.com username on it are acceptable, as well. So, if you only own the Core Rulebook and don't want to invest in anything else, just make sure you only use material from it for any characters you make.
Then again, there are no traits in the Core Rulebook and you can have 2 for your character. So, you might want to purchase the Advanced Player's Guide (where most of the traits are) or Ultimate Campaign (most of the traits from APG plus a bunch of others are in it) as well. You can make do without traits, too, though.
And, like others have said, there will always be the usual pregens available onsite. If you play a pregen, you can still apply the chronicle sheet from that play to one of your characters--even one you haven't made or registered yet. Chronicles are the sheet you get at the end of playing a scenario that shows how much XP, gold, etc. that you got from playing it. That's how you track your character's progress, equipment, etc. as he goes through his career.
Actually, for traits, you can get some from the free web enhancement:
According to Additional Resources, it's PFS legal (except for a handful of specific traits). Definitely worth getting so you can add those two traits to your character if you're building a Core-only character. (And you can certainly build good viable characters that are Core only.)
The only campaign traits allowed are from the PFSGOP (linked above). Since it also guides you through chronicle sheets, factions and character generation, let me be the third to recommend getting your free copy.
Also if PFS is all you are doing, you will level up at the end of the first day, and potentially the second (barring unfortunate events.) If you don't bring a 2 or third character, it can save you some sleep to have the second or third LEVEL versions handy :)
Mostly you just need bring what you need to have some fun :)
EDIT: your/you're FREE :)