To add to what everyone else has said, spend money on training rather than on kit. I'm a wilderness first responder (in date until Feb 2021) and have held various quals since 2001.
With the right skills, you really don't need much kit. For anything remotely serious, your job, 99% of the time, is to stop it getting worse, to control the scene and to help get an ambulance here ASAP. I've been unlucky enough to be on scene for a bunch of incidents over the years and have only ever used gloves and Israeli dressings in anger. My car kit is based around this experience, it's gloves, tape, steristrips, a field dressing and a CPR mask plus a bit of celox gauze, a couple of ambulance dressings and a triangular bandage. I've got a couple of chest seals in there but I don't ever expect to need them. The best thing I've done is generally stop other people faffing about and to make sure that the ambulance team know where to get to. Although, I did once ID a landing zone and then marshal an air ambulance but that's a different story.
Anyway, I love cool kit as much as, if not more than most, but f you're not qualified to use it, don't carry it - I'm looking at airways here in particular.
As for the original question, for airsoft I carry a really small kit with, gloves, tape, steristrips, tweezers, tick removers, antiseptic wipes and a triangular bandage (wound packing, wiping up blood, stabilisation etc).