Hi everyone!
This is the build I play with Jarvan IV.
I've been trying different builds before making my own, and it is only with this one that I finally had fun with Jarvan.

It's a tank oriented build, but still dealing good damage, which was the most important thing for me as a jarvan ==> Go in and trap your enemies, deal as much damage as possible while your allies kill them, and go out alive.

My average score looks more or less like this: 10/5/20. This I only say in order to help you see the role that Jarvan can play in a team with this build.

I won't explain all the skills, and how to use them because i think it is quite well explained in Jarvan's Champion Spotlight video made by Riot, which you can find on Google very easily.

I hope you'll enjoy this build. Feel free to leave comments in order to help me improve it if you think that something is wrong with it. Thanks.

Well, nothing special here. Armor pen. + Attack speed, because I get enough resilience from the masteries + Demacian Standard passive... So I wanted to deal some damage. And Magic resist because you want to have some early game. I also put one flat health quintessence, so it gives me just enough HP to start the game with confidence.

Greater Mark of Desolation X9
Greater Seal of Attack Speed X9
Greater Glyph of Magic Resist X9
Greater Quintessence of Desolation X2
Greater Quintessence of Health X1

Defense tree:

I've been trying different kinds of masteries without succes, dying all the time because I was too squishy. Then I though: "****, enough with that, let's try tank masteries with dps items." Well the thing is that I don't play anything else now.

I think there is nothing special to say about the masteries here. I take Magic resist but only 1 point in armor, because your flag will almost always be on when fighting, giving you armor bonus.

Dodge, because you'll often be in melee => more survivability.

One point reducing the damage of creeps, so that I don't die early game when running after my low-life enemy.

Offense tree:

Crit. percentage + Attack speed and Exhaust improved.

I also improve Ghost, so that I can run faster from a lane to another when allies are in trouble, or when chasing enemies.

Here's the list of item I purchase(Note that the order is not necessarily the one in which i get those items all the time. I adapt according to the situation, and so should you.):

I get this to start the game. Hp, lifesteal and dmg= great.

If I ever need to go back, I buy and maybe Null-Magic Mantle as well, or directly Mercury's Treads.

When I have the boots, I buy . It gives damage, armor pen and cooldown reduction. So it's perfect, because you want to have your ulti ready as often as possible.

Once I bought the Brutalizer, I start buying the items in order to make a Tiamat. I don't see a lot of people using this item, but I thought: "why not? After all, I get in many fights against more than 1 enemy... it could be interesting".
I usually try to start buying the Pickaxe, but sometimes I buy the Faerie Charm if I see that I need a lot of mana, or Rejuvenation Bead if the game is not going very well. These items don't make a big difference, but still.

Tiamat's passive deals 50% of your attack damage in an area around you. It will allow you to farm creeps easier, and will be interesting in teamfights as you will probably jump often on the enemy team and attack.

If the game is going well, I buy a Phage and then a Sunfire Cape. Just a little more survivability and more damage. The Sunfire Cape + Tiamat will allow you to deal a bit more zone damage in a melee. Add to this the fact that Jarvan deals a percentage of his target's life at his first attack on them... If you switch targets in a melee you can deal very big damage to everybody.

If the game is not going so well... because the enemy's fed or whatever... you should adapt your build and buy a Banshee's Veil if there are a lot of casters, or a Thornmail if there are a lot of AD champs.

When you got all this, you can turn the Brutalizer into a Youmuu's Ghostblade and your Phage into a Frozen Mallet. In which order? As you prefer according to the situation.

As for the Stark's Fervor, I try to buy it when I see that I don't need anything else. I think this is just a bonus for you and the team as it gives a lifesteal aura. (+ more attack speed = more damage in zone delt by Tiamat)

I think I've said the most important things about my build. Here are the pros and cons according to me:

Pros

- Good survivability
- Good damage
- You are very useful for your team
- You are very annoying for your enemies

Cons

- You don't have a lot of mana.

(This is all that comes to my mind, if you see another con, please leave a comment ^^)