Assuming everyone has rods, reels, and lines, the first thing to go into a tackle box is terminal tackle. These are the things you use to keep the bait on the end of your line. Terminal tackle can be bought in bulk or in packages with lots of assorted pieces.
You’ll need snaps and swivels, hooks, split rings, sinkers, and weights.
Be smart and buy stainless and lead-free. They’ll last longer and they’re safer for the environment.
Next in the box are a pair of longnose pliers with a wire cutter at the base, a hook extractor, a fishing multi-tool, a fillet knife (if you’re into it) and, of course—being the optimists we all are—a scale.
This is more than enough to get any novice angler started.