Starting with the shotgun is your best bet since that fire rate upgrade completely changes how fast you can respond to threats. For 40 scrap you're getting way quicker follow-up shots, which is huge when infected rush you. The pistols should be next on your list, focusing on capacity and fire rate improvements to keep the pressure on without constant reloading.

For quieter approaches, grab those bow upgrades when you can. The rangefinder helps nail those long distance shots, and faster draw speed means you won't be caught vulnerable while lining up your shot. Something worth noting about the hunting pistol - that damage upgrade turns it into a real problem solver against armored enemies and clickers, saving precious ammo in tough spots.

If you're taking on longer range encounters, the bolt-action rifle's scope upgrade is basically essential, letting you clear areas from safe distances. Good to remember that the basic pistol upgrades work great for both the semi-auto and military versions, so don't worry too much about which one you're carrying. Just avoid wasting scrap on that revolver scope since it's not actually available - stick to the rifle for your precision shots instead.

Mix and match based on your style really - stealth players should probably focus on bow and hunting pistol first, while more aggressive approaches benefit from shotgun and rifle improvements early on. Most important thing is picking upgrades that match how you like to play.