Bounty Hunter is one of the strongest offlaners in the game that turns into a fantastic roaming ganker when he hits level 6/7. Your aim in the offlane is to acquire levels and a few creep kills using Jinada. Above all, you should aim not to die while doing this.
Skills
Get one point in Shadow Walk (to stay safely in experience range) followed by one in Jinada (to secure last hits or harass).
Max Shuriken Toss after that, until level 6 when you get your ultimate, Track.
When you hit level 6/7 rotate to mid or the safe lane under cover of Shadow Walk and gank.
Mid-game & teamfights your goal is to Track constantly and help burst down enemies.
Your combo is: Shadow Walk > attack (with bonus damage and slow from Jinada) > Track > hit > pursue/Shuriken Toss.
Items
You are fairly item independent. Do not afk farm; go ganking when you get your ultimate. You farm on heroes using Track not creeps!
Starting items: Stout Shield, Tangos, 2x Branches, Healing Salve.
Core items: Bottle, Phase Boots, Magic Wand.
Situational items: Orb of Venom, Medallion of Courage.
Post-Core potentials: Drums of Endurance, Vladmir's Offering, Black King Bar, Orchid Malevolence, Heaven's Halberd.
Luxury late-game items: Assault Cuirass, Desolator, Monkey King Bar, Skull Basher, Abyssal Blade.