You don't need to bring anything.
You're perfectly welcome to learn by hanging out, watching, and asking lots of questions.
If you have a camera, bring it.
If you have a camera but no lighting kit, bring your camera and there's a very good chance that other members will let you experiment shooting using their flashes.
If you have a strobist's lighting kit, bring it.
This is a strobist's meetup, after all. Bring your lights, stands, triggers, and modifiers.
(NOTE: it's not a bad idea to label things with your name and phone number!)
If you don't have a strobist's kit, consider buying one.
If you already have a camera and a hot-shoe flash (the kind that attaches to the top of a camera), then you can outfit yourself with everything you need to start strobing for under $70. If you don't have the flash, you can get one for under $90.
DON'T bring your $10,000 Profoto lighting setup.