Bring a plate, a spoon (forks are superfluous), and a dish or drink to share. Or not, just show up and eat. But if you don't bring anything, I can't guarantee some potluck zealot won't give you a disapproving glance.
PLEASE tell us you're coming or if you want to come so we know how many people to expect. The space comfortably holds 25 and uncomfortably holds 40. If there are more than that, we'll make "arrangements".