Jay, Most of your basic first aid kits only treat cuts and scratches (not wounds). I would get a basic kit and add pressure dressings (abd pads, kerlix, coban, ace wraps, silk tape), sure clot (good for in the pinch) and some airways. Oral and nasal airways are easy to use (nasal are easier, no measuring). Make sure you have some KY jelly if you use nasal airways. I forgot to list that.
Sutures and surgical tools are useless if you don’t know how to use them properly. You could keep a pair of hemostats to clamp off a vessel if there is bleeding.
IV fluids are a must if you know how to start an IV. Meds are great if you know how to use them. You can get a drug book and read about the meds and learn what they are for and the correct dosages. Some of these meds can be very dangerous if not administered properly.
Another good reference to have is a PDR (physician desk reference). Use it to study on the common illnesses and situations you may face in a SHTF situation. Diarrhea, vomiting, bacterial infections, fungal infections. These tell you signs, symptoms, treatments. A very valuable reference tool.
I would never recommend someone to do something they are not trained for, but in a SHTF situation, you may be all that’s there.
Check with your local fire departments and Ambulance services. They offer classes all the time. Take CPR and ACLS classes. You will learn a lot. Take trauma classes if you can find one. Check with local hospitals and see what classes they offer. All the guns and food in the world wont matter if you can’t treat common infections.
Stay current on your tetanus vaccine and immunizations.
Sorry for rambling, just jotting things down as they pop in my head. Please feel free to ask any questions. I am more than happy to answer anything I can or point you in the right direction if I can’t.