This guide might not be the best guide in the world but it is kinda awesum! :D

To start with i'm going to put in some epic wins:

When i play Jarvan IV, i always start with a healing potion and a Regrowth Pendant.
This is for staying in my lane for a longer time than my foe, to underlevel him/her and earn much more gold than him/her. That is also one of the reasons i have Teleport, so i can my stuff and fast teleport back.

If u are an unexpirienced Jarvan player, u might want to know that if u use Demacian Standard u can use Dragon strike to jump forward to the Demacian Standard, Though Dragon Strike has to be in range to the Demacian Standard and for early game i usualy press:
Demacian Standard -> Dragon strike directly after eachother to make the target fly up in air and deal much damage so they become frightened.
I dont think they have a global cooldown, just that dragon strike is a little bit delayed, this should be done like the entire game, so you just keep practicing! =)

In early game its important to get minions kills AND to make your foe fear you.
You should not get out of mana to often because of the Philosopher's Stone and runes so u can start using your abilities to get ur foe to either, die or go back to get hp so u overlevel him.
The ability rotation should be like this: Demacian Standard -> Dragon Strike -> Autoatack if he runs -> Golden Aegis -> run away from foe.
This should take him to, about half his hp.
U can also use Golden Aegis earlier if u think u can kill the foe... Kinda obvious...
However, if the foe is a better 1v1 champ than you, then you're ****ed xD

Now you should be really awesum and hit hard! Dont initiate teamfights yet though, you dont have to much hp yet, but if you are so fed u already finished the build, then u can skip this part... But don't, because thats pretty rare to get that fed... So just continue reading!
A good combo with Jarvan in 3v3 (My opinion) is Malphite and Xin Zhao because with them all can charge in at the same time and then land a cataclysm, and then BAM! 1 target dead in the blink of an eye!
The ability rotation should be the same as in early game now but u wanna stick to team on ganks and not try to solo. (U got great KS abilities you know!)

Now u should be REALLY awesum and should have a both Warmog's Armor and Atma's Impaler, the last item u get u can decide urself, maybe thornmail to maximize ur damage and get that nice tanky armor... I dont know! I usually win at this point! :D
Now u can initiate teamfights! Late game is really fun, and u should basicly do what u have done since early game :)
Thanks for reading my guide! I hoped u liked it.

Now its time for kirby dance!
<(^.^<) <(^.^)> (>^.^)>

U might downvote now and say GTFU NOOB, U DONT HAVE FLASH! (...)
I don't see why its needed! If u need to escape u can always just put up a Demacian Standard on the otherside of the wall and the Dragon strike to jump right over it! + It doesn't have a long cooldown like flash has! :)