A new build focusing on allowing Jax to become unstoppable and getting 20/0 as you should be.

Greater Mark of insight is quite self explanatory as Empower and leap strike both are Magic damage so with the extra spell pen both abilities will increase significantly.

Greater Seal of Evasion gives lovely dodge to have counter strike up permanently to cause some serious damage and stunnage(;P)

Greater Glyph of Potency is used as I think it is the most beneficial as it gives empower and leap strike a very nice damage buff early on.

Greater Quintessence of Evasion see Seals

OFFENSIVE:

Archaic Knowledge is indispensable.

Archmage's Savy gives you AP and to open archaic knowledge you have to give 3 points to it.

Cripple i open it because there's Exhaust in my spells.If you are not going to take exhaust then give 1 point to deadliness.

Other offensive masteries are useless for Jax except Havoc but you have to sacrifise 20 points to open it.

DEFENSIVE:

Hardiness is important to have more survivability until you have your dodge chance is increased.

Give 1 point to Resistance in order to open nimbleness.

Evasion gives dodge chance.Do i have to say more ?

Nimbleness as i said before you have to open it.

Veteran scars for lovely early game hp

Ardor for very nice AP/AS boost

Tenacity to help you survive longer to get more kills

Recommended:

Flash- Good but you can use leap strike to "flash away"

Ghost- Very nice to keep up to anyone

Exhaust- is my favourite as it helps to get you the kill so much

Ignite- same as Exhaust

Heal- Just incase you think you will have problems with surviving.

Anything else is just useless.

PRO
Great at 1v1
Skills are dealing huge damage
High damage output in early/mid/late game
AoE stun
High resistance to auto-attackers
Can go solo,duo or 2v1 if there's a jungler
Great ganker
Pushing won't be a problem
Can go with most of the champs



CONS
Not so much variations of his skills,maximum 3 or 4
Focused in team fights
Can be killed with CC effects easier (not easily).
Item dependent (only the first 3 items)

Boots of Speed or Cloth armor you can choose first but I like to pick boots of speed as Leap strike is your only harassment it's necessary to get out asap to not get hit much.

I normally buy 3 health pots but if you find you are harassing alot with leap strike then buy 2 health pot and 1 mana pot. Otherwise 3 health pots will keep you in lane for ages.

Ninja tabi is a must for the huge dodge chance to make counter strike never not available.

Guinsoo Rageblade is very cheap and very good as when stacked gives over 90 AP which for 2235 gold is very insane. Plus the AD and nice AS.

I see alot of Jax's get Hextech before Rylai's but early on you tend to lack many counter strikes so making leap strike have a snare with exhaust will never let anyone get away.

Hextech gunblade gives both AD and AP increases empower and leap strike significantly again self- explanatory

Atma's impaler gives more AD for more HP and your passive gives you plenty of hp this should get you around 60-70 AD while giving Armor as an extra.

Lastly Rabadon's deathcap as the AP on it with the passive can increase counter strike and empower well. A Infinity edge or bloodthirster can be gotten here instead but I prefer rabadons as it should increase your abilities damage more.

Empower should be used just before you leap strike. This will proc empower as the leap strike hits doing huge burst damage. Early game as the CD is long try to exhaust and auto attack untill your CD's come off.

It should be easy to last hit minions as you can use empower for a low mana cost to ensure to get the minion. Try to stack up your ultimate while killing minions for huge AS to farm easier.

You should see scores like this if you follow my guide. I have higher just my scores for today <3