In Tomb Raider 2013, there's a simple way to earn extra XP and salvage.
1) At the start of the game, you can hunt in the forest to gain XP. Jeep fast-travelling back to the forest to hunt out more creatures and gain XP.
2) Go to the multiplayer menu and set up a private match. Choose the Beach map while selecting Rescue Mode. Choose the Survivor Team and select customise Loadouts. Select the option at the top and choose 'Second Wind' as the Offensive skill.