As Runes i suggest:

Marks: Greater Mark of Strength. You need the extra AD at the very beginning when you're jungling. This way you clear the jungle more easily and increases you damage when ganking.
Seals: Greater Seal of Resilience. The bonus armor at lvl 1 is super. Jungle creeps do less damage on you and you can take some more hits.
Glyphs: Greater Glyph of Shielding. This is my choice, i don't think i need the magic resist at lvl 1. The jungle almost only does physical damage, and the ap carrys get stronger during the game, and this way so does your magic resist.
Quintessence: Greater Quintessence of Strength. Just like the marks bonus AD for faster jungling.


Other options:
Marks: Greater Mark of Desolation. The armor pen is nice, but i still prefer flat AD
Seals: Greater Seal of Fortitude, Greater Seal of Vitality. The Health and Heath per level are other options for the Seals, but my choice is still for flat armor.
Glyphs: Greater Glyph of Warding. It's pretty much an equal battle between MR/lvl and flat MR. This is a nice 2nd choice for glyphs, it's your choice if you want flat MR or MR over lvl
Quintessence: Greater Quintessence of Desolation. Really much armor pen on this one, i prefer the bonus ad for easier jungle in early game, but the armor pen is super for late game. Your choice again :)

For Masteries I take 29/1/0
I just take the mastery bonusses for smite and ghost, all the AD bonusses, increase of damage dealt, Cooldown reduction to spam empower more often, magic pen for the extra damage of all your abilities and armor pen.

First I pick cloth armor and 5 health pots, just as any other jungler. Try to rush for madreds razors and boots of speed for fast jungling and better ganking.
After that, (depending on the team you play against) pick up mercury threads ( or ninja tabi if you play against heavy ad team) and wriggles lantern. Then pick up trinity force, start with sheen. After the trinity force you should get a rageblade, which stacks super with your passive.
Then you do enough damage for now. Get a warmogs armor for health, then an atma's impaler. If the game isn't over, you should sell your wriggles lantern and buy a maw of malmortius.
Now you do heavy damage and you are hard to kill.

Firstly, take a point in counter strike. You can dodge attacks from monsters in the jungle and stun. the stun is super when you are ganking. I usually take empower as the second spell because it refreshes the autohit timer, so you can put out more dps. If you want to gank at lvl 2, consider getting leap strike at lvl 2. It's amazing when ganking. At lvl 3 pick the last ability you still don't have.
I prefer to max empower first for maximum damage. Max leap strike at lvl 13 and counterstrike at lvl 18. Of course you take grandmasters might ( ulti ) at lvl 6, 11 and 16.

As summoner spells i take ghost and smite. You can jungle jax without smite, but that's really slow and it's no fun. I prefer ghost above flash, because you can jump with leap strike to an allied champion/minion/ward as well as an enemy.

Other options instead of ghost:
Exhaust: It's the second best option in my opinion, i prefer ghost but exhaust is a nice stand-in.
Ignite: Who needs ignite when you are jax. You put out so much damage nobody can heal up against.

I hope you guys like my build of jax.

Good luck owning the sh*t out of people :)