For our first big trip we have just come back from, I made us up one using a small kit I had here, had all sorts of bandages, slings, needles, saline, cold packs, tape, etc etc etc. To that I added panadol (if you have littlies don't forget kids panadol, ours are old enough to have normal panadol crushed up though), nurofen, sedatives in case I got migraines, sons epilepsy meds, my anti-baby meds, aloe vera gel, stuff to stop the trots, gastrolyte for if the kids got the trots, stingoes, stop itch, bandaids. If you do have perscription meds, pack repeats. We would have ran out as we extended our trip, but I had repeats for both of us in the glove box.
The only things we had to use were a needle for daughters splinters, and mountains of stingose - daughter got hit with jelly fish, and we didn't have any vinegar, and stop itch. But best to be safe then sorry