Don't settle on a stealth mentality. The game doesnt necessarily want you to. I did so and it drove me batshit insane. It's a survival game not a stealth one.
This becomes abundantly clear in some places like
Bill's Town and Winter
Stealth merely gives you an edge but you will need to spend the bullets you save on some enemies.
At the end of hard I had so much ammo I could have killed a whole wave of clickers and bandits and still had some ammo to spare. Survivor is turning out the same way too.
Be smart with what weapons you use and you should get through just fine. The game hands you ammo when you really need it.