Medicine is a very broad subject. It can extend from the simple basics of home first aid, all the way to bleeding-edge technology in dealing with neurosurgery. So while it spans a great deal of territory as a subject, it is still held in place by a plethora of common threads.
One of these such threads is the motivation to help another. Medicine can often be unpleasant and messy (not to mention stressful), but if the one practicing it really wants to do some good, then that motivation will prevail over the unpleasantries.
Another common denominator is that of preparedness. This is actually the crux of good medicine in any form. For example, say you were out on a hike and fell and broke your leg. All the medical knowledge in the world wouldn’t help you if you were not prepared with the right equipment. And vise versa. All the fancy tools and bandages will do you no good if you don’t know how to use them. So good medicine is composed of preparedness in terms of both equipment as well as knowledge.
This is why if you are going to try your hand at first-aid, you need to be sure to buy the necessary items so that you can have the equipment needed to hand in the event of an emergency. You never know when you will need bandages, splints or even a stair chair.
So how many kits does one need? Well, how many places do you find yourself? First-aid kits should obviously be found in the home and one in the car. One at work and then anywhere else as applicable.
Another item that one should have is a manual of their first aid techniques. Since one isn’t going to use these practices all the time, then can get stale in the mind. Having a quick reference guide to refresh one’s memory will also come in handy.