Jarvan is a good dps, and also can be a good tank if we buy items for being a tank ;)
But in this build i'll show you how to be a good dps and be semi tank to don't die fast in game :D

Quint's for health are usefull in early game, because it give nice boost. Armor penetration marks give's about 15% armor pen so it's so good al the time. Someone would be angry on me by choosing seal's and glyph's for mana reg. Why i have choosen them? Cause we can spam our skill's often without buying items for mana regeneraton :>

Masteries almost standard for dps's.

Items... First of all, i prefer buying doran blade. It gives nice boost in early game. In the middle of game, when i have some lifesteal i selling it.Boots of speed(we need to be fast) Madred's gives us some armor,a lot of atk speed and some ad, but what is most interesting, is unique passive(everyone know what is it ;] ), next i'm getting atma impaler, it boosts our defense, give some critical chance and great boost for ad(especially in late game or when we gain frozen mallet). Frozen mallet(lovely slow),boost to hp(what gives us bonus ad because of atma's passive). Hextech... some ppl will tell me that i'm noob or sth like that. But why i'm choosing it? Because of nice ad boost,lifesteal and... unique active! additional slow like exhaust with 60 seconds cooldown ;>
last whisper for armor pen boost. Of course we can use another items, but the most important is boots of swiftness,madreds and atma. If we have on the lane only ap champs, we have to buy force of nature(greatly increases our magic defence) or if we have ad,this items which i shown will be enought good :)

Demacian standard first. It can be used in early game to show ppl covered in bushes ;] Next dragon strike, to harras and make a lot of dmg. next get golden aegis. Use combo:throw Demacian standard behind the enemy,use quickly dragon strike,make normal hit,use golden aegis to slow enemy,normal hit,and if the enemy champ is still not killed,use cataclysm to end his life ;>
In almost pvp 1 vs 1 you will win at 99% success rate. 1% is reserved for a mistakes of trying to kill tank, or some kind of unluckiness ;p

Ghost- good to catch escaping enemy or to run out when we see that we have no chance to win ;p
Heal-always good!

Jarvan, is good harraser and win almost of pvp's. What is more using demacian standard and dragon strike can protect our life by using it to escape. This skill's usage give us the simple effect like cassadin ulti, or ezreal/tryndamere skill. If we use wisely our skills we will own most of the games ;]