This is my build for Jarvan IV, also first time making a build. Basically I made him into a Tank/Dps. A common build for Jarvan, and in the sense its the same as the recommended build except with added tweaks looking more into damage and critical hits. I also want to add that updates will come once I get my rune page to my liking.

i will like to add that this is currently the page I have, and I know I can make it into what I want. I will update as soon as I have everything to my liking.
I wanna concentrate here mainly on Health, and Mag.Rest. I wanna add more health in the future. Of course add Atk.Pen, and the extra damage comes in handy. And finally that extra crit damage is added, well because I got it from the Combine runes page. lol

Heavy on ATK, and the rest on Def. I usually have it on this set for any dps I use. Since Jarvan is already tanky I concentrated on ATK here.

I start of with tank items because I wanna make sure I can make it through a battle before I do main damage. Grabbing regrowth pendant helps me lane a letter better, and not worry about health so much. I gotta say this depends a lot on skill. Eventually getting Warmog, and Merc. Threads you should work into Attma's Spear. Actually before the spear you should have 2kills, but added the spear another 3 are insured. At this point the game might be over, or you're looking into an epic match. Where the rest of the items maybe purchased depending on the outcome.

Demacian Standard is a must. Its a scouting tool, and buff, also deals dmg with a longer and wider range. Concentrate on this skill and become better with it since it also sets up the combo E,Q. Looking into E,Q deeper. We all know it knocks opponents upward, but also its a great escape combo. Be quick and know where to place the flag. Cataclysm, or Demacian ***breaker, is the ace in the hold. Capturing opponents for your team or even dealing the killing blow. So much can happen with this skill. Initiating and defending is your key goal here. Know your roll as a T/Dps. Tank first.

Flash and Ignite.
Extra escape power, and the extra damage is good. You know how it goes.
Change it if you like, Exhaust is neat for those that Flash away from your ult.