In the army we carried a tourniquet, an israeli bandage, and a thermal blanket, and honestly if your concern is survival, anyhing more is just extra weight.
Since then I've gotten a degree in emergency medicine and built around a dozen medkits formyself and other. At the moment I have two medkits I actually use. A small IFAK type one I take with me to the range and innawoods, containing:
>a tourniquet>a large roll of cheap gauze>an israeli bandage>duct tape>small flashlight>two (2) space blankets>some loose prep pads>a sterile scalpelThis covers pretty much every possible survivable accident from minor cuts to traumatic amputation. Does it cover them in the most efficient and aseptic manner, no. But its realistic for field conditions and the whole thing fits in the back pocket of my jeans.
The second one is a large tear away type I have on the back of the head rest in my car, and inside I have collected pretty much all sorts of junk from ampules of nacl to hello kitty band aids, without forgetting the essentials of course, easily accessible.
Over the years Ive come to the conclusion that the best first aid kit is the one you actually carry with you and know how to use. Having a big ass med kit with chest seals and ibuprofein is nice once you need it, but are you actually gonna take it with you? Leave that shit in your car so that once you need it, its propably a couple minutes away from you, also seeing accidents on the road becomes a lot more exiting lol. Just don't be that goy who carries around a pneumothorax needle and doesn't even know how to palpate ribs.
If you're looking for places to buy your gear, this was what I choce for EU countries a couple years ago atleast. Had best prices and shipping, long expiration dates, actual brand gear and suprisingly no jewery.
https://israelifirstaid.com/ 