Guerrilla Scavenger is a resource gear perk that gets you extra gasolina, metal and medicine when you loot. It speeds up gathering the materials you need for crafting.
Every time you pick up these materials, you get more than usual. You hit crafting costs faster.
Good early when you are short on materials. Later on, a defense chest perk usually helps more.
Observant lets you collect loot from further away.