Hi this is my first build, but I'd like to share this with people since I do so well with it :)

I was looking at some guides and I gathered the best items of what is the best thing for Jarvan. I play him as a laner, not a jungler so this guide will be for a laning Jarvan. The way I play Jarvan is that I make him as durable with survivability with a punch and killing power.

Pros
Great CC
Great 1v1
Trap the Enemy within to prevent their escape
You can suicide by ulting a group of champs, thus ensuring your allies escape
Durable
Strong

Cons
None that I can really think of

So I stack as much armor penetration as I can with the marks and the quintessences. To make myself very meaty and durable I put in seals for armor and that will make Jarvan very durable, especially early game. For the glyphs, I put in cooldown glyphs to reduce the time it takes for the skill sequence combos needed later.

I pretty much put in quite a bit of offensive masteries even though I prefer to have more utilities for regeneration. I am not going to explain this very much since an offensive champion needs offensive masteries.

Ok, I took some ideas from SinJustice so I give him some credentials. However he went a different route than I do so that is why I decided to create this build. I start off with a Regrowth Pendant and a Health Potion to start off. This will allow you to stay in the lane for a long time to gain experience, farm, kill, and withstand harrassment with the potion if you still want to stay in the lane with low health. The next group of items can be bought in any order but I will explain the importance of them. The philosopher stone is all about the sustainability of Jarvan to stay in the lane. I like getting the Heart of Gold early because that will allow you to get a faster income. Eventually you will get to the Shurelya's Reverie and Randuin's Omen, which I like getting first because that will make you a very beefy champ with good regeneration. Also if you are involved in a fight, you can either run away or chase with the Shurelya's Reverie and lower the attack and movement speed of the enemies with the Raduin's Omen. Also get the mercury treads to make sure that you have that tenacity. Also if the other team is more AP than AD then I would replace the Randuin's Omen with a Force of Nature. After you established those items, I go all out damage items. First off I get the infinity edge and that drastically increases your damage output. The I go get the life steal of the bloodthirster. By this time the game is probably done, but if you are still playing I get the zeal for the trinity force, which is a game changer.

I will emphasize that this following combo is the bread and butter of Jarvan. I go Demacian Standard, Dragon Strike, then Golden Aegis. This will increase your armor, decrease their armor, increase your attack speed, slow the enemy, and have a good damage output as well as using the passive. Later on in the game do the same combo but add in the ultimate and you will have yourself a kill or an assist for sure. I usually use the Demacian Standard when there is a team fight or attacking the tower for my teammates. The Golden Aegis is a good way of slowing the champs if they are chasing you or your teammates or vice versa. I go the the Demacian Standard first since it can buff you and your teammate as well as damage the other champs. After getting Dragon Strike, you can get that combo of E+Q which will knock them up for the eventual gank.

You're most likely going to have to initiate depending on your teammates, but with the E+Q Demacian Standard and Dragon Strike combo, you can take most of the champs out for a second while your teammates strike, but this will put you in the middle of them and thus attacked, be ready. One of my favorite tandems is a blitzcrank that will pick off a champ and you can gank them easily.

This is all I can think of at the moment, I hope you can use this guide well and I will probably be editing this as I think of other stuff to add. Hope to see you out on the LoL games!!! ^.^