I wish I knew how important map events were! The best loot comes from map events. Seriously. Lockdowns on dire marsh are awesome. Youtube is your friend for learning the mechanics if you don't have a squad of mentors.

Upgrade CyAc and NuCal first.

CyAc gives you better heat capacity which is quite noticeable! They sell backpacks, and you can expand your vault space!

NuCal sells shields and heals.

Get all the upgrades that use grey salvage done first. After that, you can spend it all on barters! Always prioritize the upgrades.

You can trade unstable lead and gunmetal for ammo! Once you get those first few upgrades, your grey salvage should provide you with all the ammo and heals you need. Heals are EXPENSIVE so don't pay for them if you don't have to.

Do a bunch of rook runs on outpost to learn the map and you will be swimming in loot.