This has (coincidentally) been a topic of discussion within the instructor ranks at my self-defense school lately. Some of the real basic things are 4x4 gauze pads, tape, gloves, etc. These can be found in the basic kits available anywhere, Wal-Mart, Target, etc.. Some extra things I carry in my truck kit are an isreali bandage (like an ace wrap with built-in gauze pads for a through-and-through gunshot, etc), either a SWAT or a CAT tourniquet, a good pair of scissors, quick-clot, etc. Quick-clot has become way more available recently, and it is good stuff to have handy.