You need a medicine kit to be able to use a medicine skill roll on an injured person. It's your bandages, ointments and so on. Each kit is good for 10 uses. Higher quality items will normally give 1 or more raises on any skill checks made with them, so you might have a kit that cost 5 times as much as normal, and would give a +5 to each medicine roll made on it. Alternately you might say its just a double size kit, good for 20 rolls, that costs twice the normal amount. And if you had any specialised tools in there (i.e. to treat a non human) that could also increase the price