Start with your E and do the Krugs. You should be able to do the Red Buff and Raptors without any Problems. Then you can decide if you go for an gank or kill your blue buff. If you want to Counterjungle always have an ward Ready! If the enemy jungler Notice that you make his buffs jump away with your wards.
After buying Bloodrazor and Berserkers Greaves you can decide: Tanky or DMG. I often go Dmg after Berserkers Greaves with Hextech Gunblade, Cause it is better for Ganking than Guinsoos and can secure Kills with his Active. After that you should buy an tank item. Guardian Angel is a good Item for that cause it has MR and Armor and his Passive can save your life or can win a fight for you. Then build Guinsoos cause Guinsoos Passive works Perfect with Jax Passive. Your last item should be an Tank item.
TIP: If more than one Lane cant kill his opponent cause he survives Low Life all the Time, Buy Ohmwrecker to Towerdive him and finally kill him.