I know CPR and a few other necessities, and I have a typical first aid kit. I want to find or make up a kit for injuries that are more serious than a cut finger. I have gotten some info from the forum and gone on line. I find kits rangeing from $40 to $400. I have no idea what the some of the contents are. If I need it all. What's essential. Shelf life. And so on. Is there a resource recommended by you folks with experience. Thanks!