These components are gathered all around the world, and they allow you to make a variety of upgrades for Lara. You use these components to heal, craft improved ammunition, raise weapon stats, and to make larger containers for your ammo.
Byzantine Coins
These Coins are interesting because they have no actual use for most of the game (unlike the other items you find). Instead, save these Coins until you’re at the Soviet Installation. A Supply Shack on the northern side of that map has several items available for purchase. You use the Coins to acquire these items. They include a powerful Rifle, Shotgun, multiple weapon accessories, and a few personal tools for Lara.
Cloth
Cloth is used for Specialty Arrows, Bandages, and equipment crafting. Bandaging requires Cloth and Herbs, and Lara needs to do this often on the higher difficulty levels. You find Cloth in some boxes around the world. It’s also frequently on fallen enemies, so search all corpses that you come across.
Bear Hides
Bears live in deep caves and are quite hard to defeat, but they have special skins that are used in high-end crafting. Mark the location of every bear you find so that you can come back and hunt them periodically.
Feathers
Feathers are used in the crafting of Arrows. You get Feathers from bird’s nests and bird corpses, which are seen frequently in the outdoor areas of the world. Shoot the nests down if you cannot reach them manually, and search for your Feathers. You often find more than one.
Note that it’s better to shoot nests down with your Pistol or Rifle, because that ammo is easier to find compared to Arrows.
Hardwood
Bundles of sticks or birch saplings are your sources of Hardwood. It’s used to craft Arrows.
Hides and Exotic Hides
Rabbits, deer, boar, cats, and wolves are all sources of Hides. Many of your upgrades require Hides, so it’s wise to hunt animals whenever you find them. Siberian Wilderness and Geothermal Valley are both amazing locations for hunting.
Mushrooms
Mushrooms are found in Caves or in dead trees, out in the wilderness. These let you craft Poison Arrows (one of the best possible weapons for killing heavily armored targets).
Salvage
Salvage is found on corpses or in many boxes. Use Salvage to improve your weapons.
Herbs
Herbs are a healing component that you gather from red-berried bushes in the wilderness, or from baskets that are laid out in settled locations.
Magnesite Ore & 
Chromeite Ore
Caves are usually good sites for Ore. Look for veins in the well with a dark mineral running throughout them. Interact several times with each vein to harvest the Magnesite Ore that is there. Later in the game, you learn how to gather Chromeite (when you reach a specific Codex).
Ores are major upgrade components, and they’re also used to craft improved ammunition.
Oil
Once you have an Oil Flask you can collect this material from pools of oil or yellow oil dispensers. This is a vital material for crafting explosives.