Hi, Summoners. This is my first build, and it's about my main champion, Jarvan IV. Hope you will enjoy it and it will be useful to you. He is a great champion with cool skills and with incredible strength.

Pros:
+high damage in early game

+survival skills

+not to high cooldowns

+slow buff with Golden Aegis

+good farming

Cons:

-low armor and magic resist

-if stunned, Jarvan can dies easily

-quite slow movement speed

-eats too much mana

I choose Flash to Jarvan, because in case of danger it can be really useful, or after turret diving it also useful to stay alive. Or, if one of your teammate is in danger, u can flash to save him/her. Or, you can steal the baron bonus if you flash in and steal it from the enemy, gaining more gold and more strength

The second skill I chosen to Jarvan is Ignite, because if the enemy somehow can alive your skills, you simply ignite him/her and you got a kill. I think ignite is really useful. And, with healing champions, like Dr. Mundo or Warwick, it also useful, because it reduces the healing with 50%.

Ghost can be also good, because you can run away so fast in case of danger, but it don't protect you from stuns.

Cleanse can be really useful too, to stay alive when stunned, slowed, snared etc.

You have to play aggressively with Jarvan, because you are strong, and you just have to use your skills to kill. In early game, you have to kill at least 4 or 5, kill minimum 60 creeps and destroy at least a turret with your team. You can gank of course, but if you have a paper lanemate, it's dangerous to leave him alone. Sometimes you can go into the jungle to kill the Lizard Elder to get more damage and to kill the Mana Golem to get the Blue Buff. It's important, because u haven't got mana problem with it, and your Cooldowns are reduced, too. In teamfights, focusing you first can happen, because you knocking and armor reducing can be deadly, and your ultimate is strong, too.

Jarvan has really useful skills.

His passive ability is Martial Cadence. This passive makes your first hit more stronger, because it deals 10% of the enemy's current health as a magic damage, but it maximum deals 400 damage.

Jarvan's first skill is Dragon Strike. Jarvan extends his lance to deal physical damage to the enemy and lowers their armor. Really useful, because if goes trough multiple enemies, and if the lance is in contact with the Demacian Standard, it pulls Jarvan to the location of the Standard, knocking the enemy into the air. The lance-standard combination is really useful, because you can attack or rush away with it in case of danger.

Jarvan's second skill is Golden Aegis. Jarvan forges a shild to protect himself for 5 seconds. If there are more enemy champions, the shield will be stronger. Other thing, what we have to know about this skills is it's slowing effect. It slows the enemy for 2 secs.

Jarvan's third skill is Demacian Standard. It deals magic damage, gives attack speed and wards in bushes.

Jarvan's ultimate is Cataclysm. He jumps onto and enemy, dealing physical attack, and surround himself and the enemy with an impassable cage.

I use the 21/0/9 combination to Jarvan, because he needs attack damage, but some health and mana regeneration is useful.

I always build Jarvan to a heavy DPS with some health and magic resist. So i choose full damage runes, and in late game you will be the master of the game, of course if you play well. I choose attack damage per level runes, because these runes gives you much more attack damage, so you can be more successful.

First I start with the Boots with some potion, it can be blue or red, personal decision. Then I buy B. F. Sword. After it, I make Berserker's Greaves from Boots. Then I buy Bloodthirster to get more damage and lifesteal. Then I buy Philosopher's Stone to get some health and mana regen, to stay alive and to get some kills. With Jarvan, it's hard to stay alive without mana. Then I buy B. F. Sword, Pickaxe, and Cloak of Agility to make the Infinity Edge to get more damage. After it, to stay alive, I buy Ruby Crystal, Sapphire Crystal to make Catalyst the Protector. After it, I buy Negatron Cloak to finish Banshee's Veil to get more health and magic resistance, and the spell blocker bubble. Then I buy another Bloodthirster to get more damage and lifesteal, and after all, the last item is Last Whisper from Pickaxe, to get armor penetration. With these items, Jarvan is really strong.

First, I always choose Dragon Strike, because it deals really nice damage and reduces armor. Then I choose Demacian Standard, because with it I can look into bushes and it deals damage, but it's not too big in early game, and the main reasons why I choose it is the bonus attack speed and the knocking effect in case of contact with Dragon Strike. The third skillpoint is also Dragon Strike, but the fourth skillpoint is Golden Aegis because of the slowing effect, and it protects me from minimal damage. Then I put skillpoints to Dragon Strike and to Demacian Standard. Then, at level 6 I put the skillpoint into Cataclysm, to Jarvan's ultimate. It is a really useful skill, because it deals quite big damage, and in the impassable terrain you can easily kill the enemy, if he/she has not got teleport abilities or skills. Then I put 1-1 skillpoint to Dragon Strike and to Demacian Standard. After it, I put a skillpont to Cataclysm again. Then I complete the Demacian Standard and after it I complete the Cataclysm and the Golden Aegis.

-That's okay that you are strong, but avoid turret diving, because you have low armor, and don't be a suicider. No one wants to die.

-Try to avoid stuns, and CCs, because if you will be slowed, snared etc, u can die easily.

-Never go in a 3 or higher v1 battle.

-Use your Demacian Standard to look into bushes.

-Try to kill as much creeps as you can

As you see, I tried to avoid damage, so I hadn't hurt too much. I killed 177 creeps, destroyed 5 turrets, and killed 17 enemy champion. I died when I get stunned and 3 or 4 enemy started to kill me.

It's not the best match, but I think not the worst. I hadn't hurt too much in this match, too. But we won :)

So, this was my Jarvan build. Thank you for reading, and please let me know the mistakes in this build. Hope this build will be useful to you. All the best, and be successful in the Fields of Justice.
Sorry if there are some writing mistakes, I'm not the best in the English language.