Firstly thanks for checking out my guide and i really hope it helps you. I find it a great build. One thing i will say is dont expect some astronomical kill counts because Jarvans not for that. Use jarvan like a wrecking ball. in team fights Initiate and get your hands dirty then back out and let your ADC or mid lane AP/ AD get fed from the kills. He's also useful for when that enemy is about to make an escape with little to no health. You can chase him down and keep him from making a safe exit with your EQ or Ult {R]. He can take the damage while simultaneously dishing some out in return. The idea of this build is that you can hurt your enemies without too much fear of getting obliterated. You can initiate a fight and if things arent going your way you have plenty of health and CC to keep your enemy at bay while you make a timely exit. Again remember this is a very generic Rune page that i use for most of my AD's so feel free to change it if you think something else would work better.

My rune page suggestion is a fairly standard one. this can be used for most AD champs. it has a leveled amount of Armor penetration as well as Armor and scaling magic resist.Towards late game enemy AP champions are going to become more dangerous so scaling magic resist limits the affect. Finally my quints are all Health. The idea of the build is to be able to sustain and survive longer. Extra health no matter how small is always a bonus.

As you can see my masteries are more defensive. Like i said before Jarven is not for accumulating large kill counts. he's about keeping your top lane counterpart at bay and being a wrecking ball in team fights towards late game. With this build your essentially a tank. Clever enemy players normally ignore the tank and go for the ADC or AP but since your packing damage the option to ignore you is removed and they are forced to try an deal with you leaving them exposed for your ADC and AP to kill.

The item build i have listed above is bible for me. i follow it every game i play Jarvan. Mecury threads gives a boost to your magic resist should the mid lane decide to come into your lane. Ages of legion is a great item and it proves beneficial not just to yourself but to your fellow teammates. The Black clever gives a nice boost to both your health and your damage output. Warmongers armor boosts your health up incredibly making it an ordeal to try an kill you. Ruin balric boosts your armour even further and Frozen mallet, like black clever gives a even further boost to health and damage output simultaneously.
Towards late game the dorians blade is optional. i tend to swap it out for one of the following.
{Blade of the ruined king} because i like to have just a little bit of life steal.
{Entropy} for a even further boost to health and damage
{Sheen} just for that little bit of damage boost when using your abilities to initiate or CC

With Jarvan i normally start passive and just use the Q to poke at my enemy champion. Most top lane champions are more AD based and dont have much in health or armor so you will be surprised at how quickly a few Q attacks early game will force them to stay back and waste health pots. Dont try to initiate very early. i normally try hold out for level 6. Using your pop up EQ combo and your ult next to a friendly tower is a great tactic. the tower does most of the damage and allows you to easily secure a kill. Top lane champions will start to move to other lanes in the hopes of getting a kill when they cant get one from you. use this time to farm and get your tank on or even gank other lanes maybe even catch your own top lane counterpart out of position.
Towards mid game when your build is starting to take shape become a little more aggressive. Use Jarvan like a wrecking ball in team fights. use your CC abilities to initiate and inflict some preemptive damage. you should have enough health to stay fighting while your E and Q cool down. If the team fight has gone in your favour use your EQ again to stop that enemy trying to make an escape or if things didnt go well and the enemy team have come out on top you can use the EQ to create some distance and begin your own escape.
Your Ult can be incredibly useful in aiding a teammates escape by trapping their persuer just be carful when you Ult. in my early games i often made the error of trapping my teammates in the ult too giving enemy players a chance to take them out. Likewise dont use it near an enemy turret or you will become victim to your own error. PRESS R AGAIN TO REMOVE THE ARENA. just be clever about it and in a given situation be smart how you use it.
Jarvan in my opinion is an incredible champion if you play him right. He can harass and turn a teamfight in your own teams favour. He has great sustainability without needing to make a retreat. He can stand and fight while others try attack and run. One of my favourite champions and a definite recommendation to anyone who is new to league.
Hope this helps you out and if you have any opinions, recommendations, criticism {constructive criticism } or general feedback please let me know. GL HF