Hello guys!
Yesterday I played lol and I saw the worst Jax that anyone has ever seen. It's quite strange feeling when i see that my favourite champion has stats 0/20, so i wrote this guide to avoid similar situations :) I hope that u'll like this guide.

Pros:
- Good in late game
- Low cooldowns in late game
- Good escape system
- Very fast movement speed
- Easy farming
- Good demage
- Very good sustain

Cons:
- Weak in early game
- Only one cc
- Long Cooldowns in early game
- Expensive Build

Barrier - It can safe your life :)
Cleanse - WithSight Ward andLeap Strike u can always escape.
Exhaust - I don't recomend this spell. We are fast, so we don't need slow to chasing enemies, and we haveCounter Strike, so we don't need Attack speed reducing.
Flash - Good to escaping or chasing enemies.
Ghost - With this summoner spell it's impossible to caught us :)
Heal - It can help in teamfights, but i don't recomend this spell
Ignite - Good spell against champions like Mundo or Vladimir to decrease their healing effects.
Smite - Take if jungling.

21/9/0 is the best combination for Jax. In offense we take Ghost or Ignite increase, CDR, AP, AD, and armor pen. In defense we take Cleanse, Barrier or Heal increase, HP regen and HP.

Greater Mark of Attack Demage will help us in early game.
Greater Seal of Armor will help us in early game.
Greater Marks of Scaling Magic Resist will help us in late game.
Greater Quintessence of Life Steal - More life steal is always good :)

Mercury's Treads gives us more sustain and Tenacity.
Blade of the Ruined King - It gives us life steal, attack speed and deals 5% of the target's current HP, so it's good on laning phase and later too :)
Trinity Force - All bonuses of this item are good, but the best is spellblade. We love this :)
Randuins Omen - Tt gives as more sustain.
Maw of Malmortius gives us more dmg and sustain.
Frozen Mallet - For the end more dmg, HP and slow :)
Enchantment: Alacrity - Jax love movement speed :)

To be continued :)

Relentless Assault - Every time Jax attacks an enemy he gains 4 / 6 / 8 / 10 / 12 / 14 % increased attack speed for 2.5 seconds. The percentage is increased every 3 levels. This effect stacks up to 6 times. Will still stack if the attack is dodged or misses due to blind. - Good passive giving us attack speed.
Leap Strike - Jax leaps towards a target. If it's an enemy, he attacks, dealing 70 / 110 / 150 / 190 / 230 (+60% of ability power) (+1.0 per bonus attack damage) physical damage. - Good to escape with wards, and chasing enemies.
Empower - Jax charges his weapon with energy, causing his next attack to deal 40 / 75 / 110 / 145 / 180 (+60% of ability power) additional magic damage. - Good demage and low cooldown.
Counter Strike - Jax dodges all incoming basic attacks for 2 seconds and reduces AoE damage by 25% while he is dodging. At the end of the duration, Jax deals 50/75/100/125/150 (+0.5 bonus attack damage) physical damage to nearby enemies and stuns them for 1 second. This spell deals 20% (up to a maximum of 100%) increased damage for each attack dodged. Jax has the option to activate the ability again after 1 second to end the effect early. - Stun and good DMG. Useful against ADC or when jungling.
Grandmasters Might - Passive: Hitting 3 consecutive times enhances Jax's next attack for 100 / 160 / 220 (+70% of ability power) bonus magic damage.

Active: Jax gains 25/35/45 (+30% of his bonus attack damage) armor and 25/35/45 (+20% of his ability power) magic resist for 8 seconds. - More DMG and more sustain. Ideal :)

Jax is very good champion having good sustain and good DMG. I recoment playing careful in early game. If you want to play Jax you have to remember 2 things:
1. ALWAYS HAVE WARDS
2. U CAN ALWAYS CHASE ENEMY WITH YOUR MOVEMENT SPEED (maybe without Teemo or Singed). :)