The Skill Tree, represented by the Tatau, is how Jason Brody evolves. You earn XP by completing missions, liberating outposts, and performing stealth takedowns. XP translates into Skill Points, which you can spend on three branches: The Heron (stealth and ranged combat), The Spider (mobility and survival), and The Shark (assault and health). Early on, focus on skills that enhance stealth takedowns, increase health, and improve weapon handling. Prioritize unlocking the 'Takedown' and 'Chained Takedown' skills for efficient enemy elimination. Experiment to find a playstyle that suits you.
