Jarvan IV Build
Not Updated For Current Season
I grab flat health quints for extra survivability in early game, aswell as HP per level seals for late game survivability. I grab armor penetration for those heavy armored enemies and i get cooldown reduction per level, as his ultimate's cooldown is a bit long.
I get fully ranked in dragon strike first, as that is Jarvan's main damage skill. It scales on attack damage, so make sure you have enough. The second skill i get is Demacian Standard, which is very useful for both survivability and basic attacks. It gives you armor, attackspeed and makes it very much easier to get away if you're in trouble by throwing your flag down, and using dragon strike on it to pull you towards it. You can also pull yourself through walls, and knock up enemies. At level 4 i grab Golden Aegis for the shield and for the slow. My favorite skill Jarvan has is his unique ultimate. If you end up in a teamfight, this is a very useful skill to have, so i of course take one point into that whenever i can. His ultimate can single out targets aswell as block others out (as long as they're melee). This skill can also help you get easy skill at your own turrets if you use it as they get hit by the turret, and is a very useful skill to chase people down with aswell.
The first items i get is 3x health potions and boots of speed. The reason for this is that it gives me the oppertunity to stay in lane longer, catch up to enemies and get away faster if you get chased down. The next item on my list is last whisperer. The main reason i get it is because it adds to your attack damage, as well as giving you 40% armor penetration, which is very good when you're fighting heavy armored enemies, such as rammus. If you're in a game against low-armored people i would recommend getting another bloodthirster. After the last whisperer, you get berserker greaves, which adds to your attackspeed and gives you faster movement. The next item you should get is infinitys edge, which basically makes you hit like a ***** combined with the last whisperer. After that you should go for warmogs for the survivability. Next, you go for a bloodthirster, which i reccomend you start building early game with a vampiric scepter if you are struggeling to survive. After you grabbed a bloothirster and got some kills, you should go grab a phantom dancer, which really adds to your attackspeed and gives you immence crit rating. The last item on my list is trinity force, which adds a bit to everything, and gives you 150% bonus damage on your next attack after using a skill. With this build, i've crit 1500+ on target champion, and pretty much nuked them down pretty quickly.
I grab ignite and ghost, which is two very useful skills to pick up kills with. Combined with Jarvan's ultimate, they can't get away.
Hope you enjoy my build, and let me know if it works as well for you as it has done for me!
(Also, sorry for any spelling errors.)