As the royal family of Demacia for centuries, members of the Lightshield line have spent their lives waging war against any who opposed Demacian ethics. It is said that every Lightshield is born with anti-Noxian sentiment in his blood. Jarvan IV is no exception, even though he is the first Lightshield born to the age of League of Legends. As his forefathers had before him, he led Demacian troops into bloody engagements with Noxian forces, and on many occasions he has bled alongside wounded allies and fallen comrades. In his most crushing defeat, he was outmaneuvered and captured by a Noxian battalion under the command of Jericho Swain. This mistake nearly cost him his life at the hands of Urgot, but he was rescued by the Dauntless Vanguard, an elite Demacian strike force led by Jarvan’s childhood companion, Garen.
Those close to him believed that his capture changed him. Xin Zhao was quoted as saying: "His eyes never seemed to look at you, only through you to something he could not look away from." One day, without warning, Jarvan IV handpicked a squad of Demacian soldiers and left Demacia, vowing to find "atonement". He began by tracking and hunting the most dangerous beasts and bandits he could find in northern Valoran, but he soon tired of such prey. Seeking something that only he understood, he ventured south of the Great Barrier. He wasn’t heard from again for nearly two years. After many had assumed the worst, he returned to glorious fanfare on the streets of Demacia. His Demacian plates were adorned with the bones and scales of creatures unknown. His eyes bore the wisdom of someone twice his age. Of the twelve soldiers who had departed with him, only two returned. In a tone as cold and steady as steel, he swore to bring the enemies of Demacia to their knees.

Martial Cadence (Innate): Jarvan IV's first attack on his target deals 10% of the target's current health as bonus magic damage; this caps at 400 damage. This effect cannot occur on the same target for 6 seconds.

Dragon Strike (Active): Jarvan IV extends his lance through his opponent, dealing physical damage and then lowering their armor by a percentage for 3 seconds. If the lance contacts the Demacian Standard it will pull Jarvan IV to its location, knocking up all enemies in his path.
Range: 770

Golden Aegis (Active): Jarvan IV forges a shield protecting him from harm for 5 seconds and applying a 2 seconds slow to surrounding enemies upon activation. The shield adds more mitigation for every enemy champion nearby when activating.
Range: 600

Demacian Standard (Passive): Passively grants Jarvan bonus attack speed and armor.
(Active): Jarvan IV throws a Demacian standard to a nearby area, dealing magic damage to enemies in the area and granting his passive benefits to nearby allies and again to himself for 8 seconds.
Range: 830

Cataclysm (Active): Jarvan IV heroically leaps to an enemy champion, dealing physical damage and creating a circle of impassable terrain around them for a 3.5 second duration. Jarvan IV can destroy the impassable terrain by activating this again. Champions can still leave or enter the area by using teleport abilities.
Range: 650

For the masteries I go 1-21-8. I take the 1 in offense just for the exhaust, stack the defense as you can see in the tree, and then 8 in the utility to get ghost boost, the regen in mana and health, and the extra experience.

Oh the great ITEMS!!!!

This is a simple choice to start: Dorans Shield
After that I build whatever there team has most have barely more magic so I build to a 50/50 build.
Start always with a Frozen Mallet for the AD/Health
Then I usually Boots of Swiftness, but MercuryTreds aren't bad either.

Then where that Tankiness comes into play:
1. Banshee's
2. Sunfire
3. Thormail, or Force of Nature (Depends on the team)
4. Atma's Impaler finish with crit and armor!!!

Skill usage:
Try to remember in which order you hit your enemies with Martial Cadence, so you can immediately use it on them again when 6 seconds are up.

Martial Cadence can only affect a unit once in 6 seconds, so it is a good idea to target another unit or champion to activate the passive during that time.

Using Dragon Strike to harass the enemy is useful. Keep Dragon Strike off cooldown for initiation, chasing or last-hits.

Golden Aegis can slow retreating enemies to finish them off. Combine Golden Aegis, Demacian Standard and Dragon Strike in this order to finish fleeing enemies if your ultimate is not usable.
Placing a Demacian Standard increases the stats of allies as well as one's own. Remember that Jarvin IV gains both his passive's and the standard's bonus stats.

It is unwise to place a Demacian Standard before a gank. Experienced players will notice the situation and act cautiously.

Using Cataclysm to cage multiple enemies is a great way of dealing damage to them without harming your own teammates. Be careful where and when you place it, as it may not turn out to be in your favor. Using Cataclysm at the wrong time/place can cause unnecessary death to you or your teammates, for example caging the wrong enemy out or caging low-health allies within.
Consider saving Dragon Strike and Demacian Standard, so Jarvan IV has an escape technique after trapping enemies with Cataclysm. Placing Demacian Standard over an impassible wall or terrain and using Dragon Strike gives you a great way to juke and escape this tactic can also be used to help enemies escape.

Enemy champions such as Shaco, Ezreal, Shen, or other champions with a similar short-ranged teleport/dash ability (including Flash) can easily escape Cataclysm. Be aware of this when using Cataclysm on these targets.

Combining well-placed Demacian Standard with Dragon Strike can disrupt the enemy enough to turn the tide in a battle. This can also be used to chase an enemy or cut them off by pulling yourself across terrain.

Jarvin IV can have a deceptively long nuke radius. Consider using your Demacian Standard and Dragon Strike combination to close distance on a target, and using Cataclysm immediately afterwards for the nuke.

Game-play:
Cataclysm can initiate a team fight very well. If built to survive, Jarvan IV can start a team fight with great success. He also deals damage well without many items. While building him, strive to maintain both survivability and damage. A team with skills such as Bandage Toss can be used to get inside the Cataclysm and complement Jarvan IV's ability to initiate well.

Summoner Spells can really go either way, but with the tree you can get the exhaust and ghost in the tree. Sometimes depending on the teams other spells, I've taken Ignite and once I took tele to watch for bds.

I believe the best bet is to go with EXHAUST AND GHOST

In summary to this awesome build, Its very hard to fully achieve this build because many teams surrender when a Jarvin IV ****s on them! :)

Give it a shot!

Plz vote well if you like!