Pros
- Jarvan IV can be built many diff ways Tanky/ full dps/ tanky dps/ and Ap if your feeling like a troll
-He has good poke because of his passive Martial Cadence
-Cause hes naturally tanky he has ok sustain (but not the best)
-He scales well late game
Cons
-Mana problems early game
-There are solo tops that have more sustain
-Must be careful early game
-Has very extreme mana problems

I dont like typing out why I do things too much so ima make this short. I play Jarvan as a Tanky Dps building Fratmogs ( Frozen Mallet, Atmas, and Warmog's Armor not in that order) which should give u about 300 ad and 6k hp with all ur warmogs stacks.

Jarvan IV's first attack on a target deals 6 / 8 / 10 % of their current health as bonus physical damage (max 400 damage). This effect cannot occur on the same target for 6 seconds. When Jarvan uses a basic attack on an enemy he will deal physical damage equal to 6 / 8 / 10 % of the enemy's current health in addition to his normal attack. The target will receive a buff that makes the effect not proc on them for the next 6 seconds. The physical damage done doesn't increase with items similar to Sheen.
- Martial Cadence physical damage will be blocked by spell shields. The target protective buff is still applied and lasts 6 seconds.
- The debuff is an On-Hit Effect so it can be dodged or blocked by Aegis Protection.

-Jarvan IV extends his lance, dealing physical damage and lowering the armor of all enemies in its path for 3 seconds. If it contacts his standard it will pull Jarvan IV to its location, knocking up enemies in his path. (Range: 770)

Leveling up
Cost: 45 / 50 / 55 / 60 / 65 mana

Cooldown: 10 / 9 / 8 / 7 / 6 seconds

Physical Damage: 70 / 120 / 170 / 220 / 270 (+1.1 per bonus attack damage)

Armor Reduction: 10 / 14 / 18 / 22 / 26%

Dragon Strike is a line skillshot that will deal physical damage to all enemies hit, it will also lower their armor for 3 seconds. The damage will apply fully to all enemies hit. If the attack hits the flag left by his Demacian Standard ability, Jarvan will be pulled to the flag's location, knocking up any enemies he passes through. It has a brief channel time (0.2s) upon cast before it activates.
-It will break spell shields. The target won't be damaged, debuffed or knocked-up.
-Dragon Strike's damage and armor reduction will not be blocked by Black Shield, however the knock-up will.
-It will proc Rylai's Crystal Scepter 15% slow for 1.5 seconds after it hits a target.
-The skillshot is able to hit, debuff and knock-up invisible enemy champions, but it won't reveal them.
-It doesn't proc any On-Hit Effects.
-The pull from Dragon Strike and Demacian Standard can be used while snared/rooted, but Jarvan will still be snared when he arrives.

Jarvan IV forges a shield for 5 seconds, which slows surrounding enemies for 2 seconds upon activation. The shield has more health for every enemy champion nearby when activating. Cost:
-75 mana
-Radius of AoE: 600
Leveling up

Cooldown: 20 / 18 / 16 / 14 / 12 seconds

Shield Strength: 50 / 90 / 130 / 170 / 210

Extra Shield Strength: 20 / 25 / 30 / 35 / 40 per nearby enemy champion

Slow: 15 / 20 / 25 / 30 / 35%

Jarvan receives a shield that blocks an amount of incoming damage for 5 seconds or until enough damage is absorbed to break the shield. The amount of damaged blocked is increased depending on the number of enemy champions surrounding Jarvan at the time of activation. In addition, near by enemies are slowed for 2 seconds. It is immediately activated upon cast.
-The slow will be fully blocked by Black Shield.
-It won't proc Rylai's Crystal Scepter slow because it doesn't deal any damage.

Jarvan IV throws a Demacian flag to a nearby area, dealing magic damage to enemies in the area and granting his passive bonus to nearby allies and again to himself for 8 seconds.
-Cost: 60 mana
-Cooldown: 12 seconds
-Range to Center: 830

Leveling up
Attack Speed Bonus: 10 / 14 / 18 / 22 / 26%

Armor Bonus: 10 / 14 / 18 / 22 / 26

Magic Damage: 60 / 110 / 160 / 210 / 260 (+0.8 per ability power)

The passive part of this ability increases Jarvan's attack speed and armor. When the ability is activated Jarvan throws a standard on a small target area dealing magic damage to all enemies hit. The standard remains on the location for 8 seconds, giving the same bonuses as his passive to all allies near it. This includes all champions, including himself, and ally minions and pets. Demacian Standard reveals Fog of War around it for the duration similarly to a Sight Ward.
- Because the standard is considered a unit, projectiles like Morgana's Dark Binding and Lux's Light Binding will contact and affect it, therefore protecting any other units behind it from such abilities.
- The standard can be selected to Teleport to.
- It is immediately activated upon cast, but there will be very brief delay (0.2s) before the standard hits the ground.
- The standard damage will be blocked by spell shields, breaking them in the process.
-It will proc Rylai's Crystal Scepter 15% slow for 1.5 seconds after it hits a target.
- The standard won't proc any on-hit effects.

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.
-Range: 650
-Radius of Wall AoE: 300

Leveling up
Cost: 100 / 125 / 150 mana

Cooldown: 120 / 105 / 90 seconds

Physical Damage: 200 / 325 / 450 (+1.5 per bonus attack damage

Cataclysm is a targeted spell that causes Jarvan to leap on the targeted enemy, dealing physical damage. In addition, a ring of impassable terrain around the target is created for 3.5 seconds. Jarvan, the target and any units that were very close to the target will be inside the ring. Jarvan can destroy the ring of terrain by activating the ability again. Enemies can use blink, dash or jump abilities to move over the ring.
-Given that Jarvan leaps to the target, not to a location, Jarvan will leap great distances if the target teleports or blinks at just the right moment.
-Jarvan will be channeling while leaping to the target so it can be stopped by CC. The channel will be very brief depending on the distance to the target.
-Cataclysm will break spell shields. Jarvan will leap to the target, but there won't be any damage and the ring of terrain won't be created. This has been confirmed as of patch V1.0.0.116.
-It is in no way blocked by Black Shield.
-It will proc Rylai's Crystal Scepter 35% slow for 1.5 seconds after it hits a target.
-It won't proc any On-hit effects.
-There is a glitch where champions using Ghost can run through the terrain created.
-Casting Flash while an enemy Jarvan IV is midair will cage you at the place where you flashed to, but Jarvan will jump to where you were standing before flash.
-Cataclysm ring doesn't count as impenetrable terrain, so it won't proc Heroic Charge's or Condemn's conditional stuns.

Marks
I go 9 Greater mark of desolation so when the enemy team start building armour i still do dmg (self explanitory)
Seal[/col]
Greater Seal of Armor for that bit of early game tankyness
Glyph
Glyph of Magic Resist for early game mr
Quint
Greater Quintessence of Attack Damage to win early poke battles

Ok so farming is a pretty simple concept for those of us who have been playing for awhile. Just make sure u get the last tick of dmg when atking a minion. Dont auto attack that will push your lane which makes you easier to gank which is not wht you want.
Also a good combo to clear waves fast ,when you have something that resembles damage, is to drop your Demacian Standard on caster minions the use Dragon Strike through the non-caster minions tword your Demacian Standard and you should be able to clear all the caster minions, and if you have enough dmg some of the non-caster minions.

Jarvan ult can be devestating if you find someone out of position it does flat dmg then locks the enemy in an impassible circle so that you can use to just wail on them or you could use it to escape.
Usage in team fights
First dont ever ult someone who is surrounded by allies you could end up just killing your self and wasting your ult.
Also its best if you dont ult champs like Kassadin, Ezreal, Shaco, Niddale, Renekton, Jax, or Tristana.Also if they have Flash make sure their Flash is on cooldown before jumping them with you're ult.