In Chapter 2-2 in the mining area, after the cinematic where the masked person takes the man in the suit away, you will have an excellent opportunity for easy treasure. Immediately in the area that follows is a brilliant diamond worth 4,000 gold and smaller diamond worth 2,000 gold. While you are upstairs, next to the windows will be a locker that you can open that contains a sniper rifle in case you need it. Downstairs are two enemies that you should get rid of to make things simple. Then from upstairs, you can pick off the half-dozen or so enemies that are waiting for you outside with the sniper rifle. After taking care of all or most of them, run out. To your left behind all the equipment is a small red ladder. Climb it and to side farthest from you will be a chest. Inside will be the big brilliant diamond. Go back and walk past the truck with the turret, then look up towards the end of the first long red ladder. You will see a shining spot. Shoot it and the smaller diamond will drop for you to pick up. In about five minutes or less you will make an easy 6,000 gold. Quit the game and choose "Yes" when prompted. This will save your equipment and treasures. Reload, continue the game, and repeat the process. You will soon gather enough money to upgrade your weapons. To make even more money, only equip the new sniper and keep picking it up or giving it to Sheva. Also keep selling it to get extra money.
Fight through the first two packs of dogs, After the second pack of dogs you will see a stack of lumber. Climb up and when you reach the top stack, turn right and you can collect a Jewel Beetle (worth 2,000 gold). Climb down the stack and proceed forward past the train car. Turn right, keeping the train car on the right-hand side. When you are almost to the end of that wall, you can collect another Jewel Beetle on the right-hand wall. After you collect both Jewel Beetles, quit the game and save your inventory. Load the level again, then sell the Jewel Beetles for a total of 4,000 gold and play through the level again. The Beetles will respawn. The only ammunition you should expend is on the two packs of dogs and two shots to destroy the explosive trip wire. Other than that, you should not have to shoot anything else.