I wanted to make my own build that i could share with everyone. I think that Jax is a very under used and under rated champion. Enjoy :)

This build is more for those who have a team they work with. I play the D with Jax and harass a lot, And grab a for sure kill when I know i can take it without dying. Late game I can take 3 champs on at once NO PROBLEM.

When going up to a fight quickly assess who you can take out first. I use Exhaust against the stronger champ and blow away the quick kill and take out the secondary. So how this would go would be like this....

1. Use Empower
2. Leap strike to weaker champ
3. Exhaust the other
4. Relentless Assault(Ult)
5. Empower
6. By this time you SHOULD have a Counterstrike ready, use that.
7. 1 more empower should take out the weak champ IF hes not already dead
8. Change power over to strong champ.

In a 2v2 situation after about 6-10 second fight i walk away with 70%+ health

Use Ignite for those early game ganks
Use exhaust for the 1v1 when you need it to pull out the kill
Use exhaust for the multi champion battles to slow down your enemies

Jax is PRIME for jungling weak champs. Use the Leap Strike and Empower to wipe them out quickly

Get the Tabi Boots as soon as possible. By level 3 you should have 22% dodge. After you get your boots try to team up and kill enemy champs quickly. The faster you get Hextech Gunblade the better off you will be with Jax. Then you need Guinsoo's Rageblade. Your trying to stack AP and AD. Jax uses both immensely for his abilities and with equipment mastery it ups your health. Madreds bloodrazor will boost your AD and attack speed greatly. But the 4% damage comparable to their full health is great considering how fast your will be AA'ing(almost 2.5).Phantom Dancer is also going to boost your attack speed greatly. And finally rabadons, Great AP and that 30% boost.

+Way OP late game
+Great for jungling
+1v1's no prob, 2v1 late game no prob, sometimes even 3v1

-gotta watch your mana
-slow early game