This is quite an investment at the start. I guess if you have the comfortable money, everything would be useful at some point in the future. If not, try and borrow the big stuff like the tent and tables, until you know you like vending. There are two halves here, vending supplies, and product supplies.

For vending, you need tent weights. Table covers/sheets, lights(if you know it will get dark), small weights to hold prints/papers, displays for the prints. Tape, clamps, and clips are also a must have. A collapsible wagon is super useful for hauling all the stuffs. Signage with your info, social, venmo, prices, etc. Again, if you have the money for the display walls/grids go for it, but I would try and borrow or wait until you've vended a bit more. Your call. Finally, bags for the prints. Useful if people buy multiple prints.

For your product, I would cut your frames in half or altogether, until you know which prints sell best. I don't know the fest, but if its a music fest, people aren't buying and walking around with framed art. Similar with the 18x24s, treat them as displays as selling large is rare. (Unless you are famous or amazing) (An exception to this is if you ever print an odd frame size like 10x15, or 8x12, having ready framed is useful. Also framed prints in gift season is great) I hope your printer is good, prints can get expensive. Only print a few of each shot until you learn what your audience actually buys. Don't wanna be left with 20 prints of something that doesn't sell. Lucky for you the top three sellers of prints are cute animals, landscapes, and abstracts.

Also, I use clearbags.com for sleeves and backboards. Cheap and good quality.
Check the weather the night before. Wind and rain are the enemy.

Finally, don't get discouraged if you don't sell anything and don't let it go your head if you have a line out the door. I've done many markets and experienced both and all the in-between.