Most conventions already have a table cloth for the tables, at least all the ones I've been too so far. Bu,t you can definitely bring your own.
Bring tape for yourself and for others. There's always a bunch of people who forget their own tape.
You might want to do small commission on site. Keep it simple and give yourself enough time to draw it and serve customers. It's nice to have a cushion and not worry about hurrying up before the customer comes back to claim their worn. Also, make them pay before starting, a lot of people get screwed over because the person never comes back to claim the work or end up running out of funds.
Keep your first artist alley experience simple, you'll catch tips and tricks while being there and you can expand your merchandise or your table display next year.