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Far Cry 3's walkthrough consists chiefly of the single-player "story" quests and associated missions.
It's suggested that once you've liberated your first Outpost and have to travel to Dr. Earnhardt's toward the western section of the north island (for the mission Mushrooms in the Deep) that you stop and segue into Side Missions and Hunting so you can equip Jason with better gear. Head over to the Crafted Items section of the wiki and check out the upgrades you can make to important items such as your weapon holster and your item rucksack.
One last suggestion is that you don't purchase weapons and equipment from stores. You will obtain these for free by interacting with radio towers found throughout the islands.