this is a nice build but I would add a chapter for alternative item like lich bane or crystal scepter since your guide is named the king od duels :P

Also try to make your like look better by adding some coding i recommend you read this guides:

Making a Guide
and
Searz's informative and awesome-looking guide

Add coding into your guide, to make it look better. Refer to jhoijhoi's "how to make a guide" to do so. For example, {{Greater Mark of Desolation}} will result in Greater Mark of Desolation if you replace the "{{ and }}" with " and "

Alright your guide seems pretty good in terms of the Old Jax (That is before the remake), so here are a couple recommendations: (A) I would largely consider a Wriggle's Lantern in the laning build (Should be bought before Hextech Gunblade mainly due to the sustain, damage, armor, and a FREE Ward. (B) For your masteries, I've played Jax for a while now, and I've figured out he has a lot of Magic and Physical Damage. Therefore, I suggest getting points in both armor penetration, and magic penetration in the offense tree. (C) I would also consider doing hybrid penetration marks for the same exact reason. (D) I recommend this to many first time guides. Go to the top of the page, click on the tab "Guides & Strategy", and then click on Getting Started Guide. It will teach you a lot of neat tips to help you properly format your guide, and proper BB Coding techniques as well. (E) Change the voting system to comment to vote to prevent most cases of down voting for no reason what so ever. Hope I helped, and have a fantastic day!