I pretty much have comics, stickers, and prints. I havent done other merch such as pins or t-shirts because I'm trying to move the stuff I already have- this is a pic of my table from last year's MomoCon...
As for prints- it depends on how many prints you feel you need or want to sell. I get my prints from RA Comics Direct(https://www.racomicsdirect.com/racomicsdirect/)- they have a package with 75 prints for $50. Mostly all my prints are my original characters...I dont really do the fanart thing.
My main seller is the comics themselves- which is what I exactly want. Next is my prints...I have one print series which has become a best seller, so that's pretty much cool. Weirdly my stickers havent been selling so well; I feel they're priced decently.
I dont go all out with bells & whistles to "make my booth stand out"...I try to rely on my passion, and getting a feel for what my buyers want.
I have my books printed through 2 different places. I print most of my Clique series through Ka-Blam; I like their paper/stock, and how it captures my art & colors; my Ray Thunder books- and a deluxe sized Clique character guide I print through Greko Printing(https://www.grekoprinting-comixwellspring.com/) I like their thick cover stock- it makes my books look "premium"(for that AND the page count I charge a premium price).
As you can see my from my set up- make sure your items are well placed. If you have more than one book, invest in some small racks to elevate the books(they dont have to be like the acrylic ones I have). Make sure your books and other merch are noticably priced with labels so that the customers have no question what the prices are. Also invest in a card reader- especially if you have a PayPal or Square account; a lot of customers dont always carry cash...this is a nice investment that insures you get card sales AND you're not walking around with tons of money on you if half of your sales are card transactions(in case of theft).
Speaking of which- DO NOT put money in a box and set under your table; there are trained con crooks who pull scams to snatch artist's money boxes from under or behind their tables...either keep your money in a pouch/fanny pack attached to you OR keep it in your pockets.
Get business cards made. Make sure they have an e-mail address as well a social media site you may frequent; if they dont buy anything on the spot, they could possibly buy something at a later point from you online.
Bring snacks & WATER. A lot of the times con food is expensive, so you wanna have something to eat on just in case you dont have $9 to spend on a slice of pizza. I usually bring 2 large bottles of water so that I can stay hydrated- along with snacks; I stop off & eat at a restaurant once I go home for the day.
If you feel you need a table buddy, bring one with you(unless getting an extra pass will cost you extra money). If you can't, then make friends with the other artists around you; it helps if you REALLY NEED to go to the restroom- they can watch your table for a minute(just know you have to return the favor as well).
I'm not sure if this show you're doing is a small one or not. I usually recommend when starting out, do smaller 1 day or 2 day shows- you can get a better gauge of how you perform, what/how you need to do better, and what/where you need to trim the fat.
Greet your potential customers- eye contact! Practice your pitch to sell your comic, so that you use enthusiasm when explaining your book to them. I've sold a lot of comics just on the sheer act of being really hype for the work that I have on the table; if you feel confident about the work you're selling, people pick up on that and will buy it. I had a customer remember me from a con a year before when she didnt have the money and came by and bought one of my books!
Hand sanitizer- it is a MUST. I made the mistake in the first year of doing cons not having it- and the day after the final con of that year, I got sick. I now use that stuff religiously, coz people are germy af...and I cant afford to be lying in bed sick anymore from germ ridden people at cons.
If you are doing cash sales- make sure you have change. I usually get a certain amount of smaller bills, so that if some customers are paying with cash, I can give them correct change...DON'T break large bills if you dont feel comfortable with it- you might lose a sale but dont be trying to give customers change back on a $50 or $100; the only way I'm doing that is if they are buying stuff that equates to half(or more) of that amount, and also I do the eye test for the $50/100 strips inside the money as well as the watermark.
Sorry this is LONG...just a lot of advice from a con tabler!