I did medicine for 30 years in the military and as a civilian and was exposed to some of the best and worst medical training that this and other nations offer. As part of my training to become an IDC (Independent Duty Corpsman) I did weekends at Yale and Harvard’s Knife and Gun Club (University Emergency Departments). I’ve also had real life trauma events in places like Kuwait, Trashcanistan, Somalia, and Iraq to name a few.
Quite possibly some of the best Real World Training (other than the real thing) I have been exposed to was Wilderness Medicine. There are various schools and individuals out there and I will not point out one over the other but the driving factor is that you are NOT 20 minutes from an ER, you DO NOT have a full medical trauma bag but here is what you can REALLY do with what you have.
The above being said you need a basic understanding of how the human body works so that is where the basic classes come in. Stop the Bleed, Red Cross First Aid, EMT and all the rest are good primers. With the advent of the internet you can actually teach yourself advanced lifesaving fundamentals if you are really interested in knowing the topic.
I have gone from having 3 full trauma bags in my vehicle to include O2, IV’s, injectables and other fancy bits of kit down to something I can stuff in the cargo pocket of my pants. The real capability is between your ears and does not rely on your bag of tricks.