What I'm taking from this is basically anything short of a major medical emergency players should be able to deal with. Minor cuts and scrapes you have bandages and maybe some polysporin to deal with it.
For things like rolled ankles and such splints are nice if someone has the training and gear readily available in their pack but it's not necessary outside of a milsim game.
To sum it up:
Superficial injuries and things that require a precursory look and maybe 1 minute of first aid players should be able to deal with.
Major injuries and emergencies the field will have the equipment to deal with it but it's always nice to have on a player if they have Wilderness First Aid or First Responders or something like that and can respond faster than say the main base of operations who might be on the other side of the field.
PS: Funnily enough, Wilderness first aid also covers gunshot wounds but I think it's moreso for hunters and such who have a danger of being shot by another hunter. Also when I did my Standard First Aid course, we dealt with gunshot wounds and biochemical attacks which I thought was a bit weird.
ಠ_ಠLess QQ more Pew Pew
READY TO >> RACE