Slide down the path and make your way through the mountain pass. Look for [SALVAGE x2] and a [PLANT] before entering the cave, where you'll discover the 'Arid Canyon' day camp and find more [SALVAGE x2] and an [XP BOX]. You can also hunt bunnies here (and rats in the cave). Move through the cave to collect still more [SALVAGE x2]. After the scene, wiggle the left analog stick left/right and tap X or Square, then move towards the hole and proceed to the end of this tunnel. [100 XP].
You can find some [SHOTGUN SHELLS] next to the corpse (that's right...) and the [TRENCH SHOTGUN] at the end of the walkway. You can now blast through wooden barricades! Jump over the gap and head through the hole at the end of the hall (scramble up the left wall to reach it) to reach a large circular tomb. Equip the shotgun to dispatch the enemies after the scene finishes. You can collect [SHOTGUN SHELLS x3] around the grave should you get low on ammo.
Pull the large weight away from the gate with a rope arrow to clear the path. Move through the tunnel to reach the 'Sheltered Alcove' day camp, where you can find some more [SHOTGUN SHELLS]. Blast the barricade out of the way, then make your way over the walkway (and subsequently the ledges) until you enter the next building.
Dispatch the enemies here right away (one will try to reason, but they're going to attack the second after this anyway, so it doesn't matter). There's one guy with a riot shield; as usual, dodge by stepping to the right, then unload on him (preferably with the shotgun at this point). After defeating them, collect the [SHOTGUN SHELLS] in the upper left corner next to a pillar, the move upstairs (in the same corner) and kill another savage.
You can find [SHOTGUN SHELLS x2] and [RIFLE AMMO] on this walkway. Open the shutters on one side and pull the weight with a rope arrow to smash the pillars on one side. Close the shutter again and open the ones on the other side and pull the weight again, this time hitting the other pillar. At the point some enemies will start bugging Lara, so pull out your shotgun and take them out. After dealing with all of them (and probably collecting [BOW PARTS 1/2] by looting their bodies), open both shutters and pull the weight one last time to bring the bell down. [250 XP].
After this, simply rush through the hall and leap towards the rope bridge. During the sliding part, shoot through two barricades with your shotgun and another scene will play. [500 XP].