Many venues require 40# weights on each leg. Look at square 4" x 4" PVC posts (cut into shorter lengths) filled with concrete, capped on one end with washered eye bolt thru the end cap. Square posts will not roll during transportation. Attach to top frame, not the leg, with adjustable ratchet straps. Have weights an inch off the ground. Attach weights to bottom of legs with bungees. Weigh the weights and record the weight on each weight. Use table leg extenders out of PVC pipe with cross bolts, not in the center. Have two lengths in same piece. As 4" and 6", or 6" & 8" . People do not like to look down. Thirty inch tables are too short. Have emergency plastic drop cloths. Have a light weight trashcan.
Have a light weight toolbox of supplies: duct tape, scotch tape, rubber bands, thumbtacks, string, sharpie pens, anything else that pertains to what your're selling, batteries, small parts that are easily lost, paper clips, scissors, box cutter, extra extension cord if usuing power, flashlight w/good batteries, tent patching kit, paper to record what you forgot for NEXT time, price tags, chemical hand warmers if cold weather, simple first aid kit: bandaids, tylenol, alcohol swabs, burn cream, insect bite swabs, Q-tips, personal medications, toilet paper, hand sanitizer. Don't forget that you will be in a strange place, eating strange food, sleeping in a strange bed and parked maybe a half-mile from your tent! Buy a bigger box than you think you need. It will get bigger as time goes by. Be prepared. Have fun!
Take plenty of water and food. $2 a bottle for water gets EXPENSIVE.