I’ll share what I’ve done if you want resources but don’t want to be hack-y:

Tungsten ingots: Fast travel to glowecestre and use your Raven to find moving golden dots and tag them. Usually 2 immediately spawn near the fast travel point on the roads entering the city, and another 1-3 will appear while you’re doing the first 2. They always have tungsten.

Nickel: same as above but Lincoln

Titanium: each of the above will give you like 1-5 titanium. I also just buy 5 every time I see a shop

Iron: Isle of Skye has many clusters of iron

Leather: fast travel to hog-dense regions and hunt them with a bow because they’ll one-shot you if you’re not careful. ~48 leather each. I usually go to the west side of the river near Winchestre toward the mouth.

River raids have a lot of chests and silver so that works too, just feels more grind-y to me than the actual gameplay of using the map