On my first playthrough I kind of realized halfway through that it's alot easier to manage if you keep at it from the start but you really need to focus on clearing infestations for morale, visiting all survey areas and narrowing down your looting runs, hit all military checkpoints and police stations for guns and ammo so you can help those calling for help. If the risk isn't fatal then you can usually manage to ask for medicine (or something else) as return. Grind out your influence so you can trade, sometimes in hard times you gotta spend a few hundred to pick up a couple rucksacks. The biggest thing is to make sure you scavenge everywhere, and don't move more than once from the start of the game if you can help it (that's why I started a 2nd playthrough with more knowledge of the game). There's no direct way to make medical supplies such as add meds to your resources without rucksacks or outposts but if you mean Bandages and Painkillers, yes, You need someone with medicine I believe, perhaps not even, make sure your infirmary is upgraded if it's achievable.