As the royal family of Demacia for centuries, members of the Lightshield line have spent their lives waging war against any who opposed Demacian ethics. It is said that every Lightshield is born with anti-Noxian sentiment in his blood. Jarvan IV is no exception, even though he is the first Lightshield born to the age of the League of Legends. As his forefathers had before him, he led Demacian troops into bloody engagements with Noxian forces, and on many occasions he has bled alongside wounded allies and fallen comrades. In his most crushing defeat, he was outmaneuvered and captured by a Noxian battalion under the command of Jericho Swain. This mistake nearly cost him his life at the hands of Urgot, but he was rescued by the Dauntless Vanguard, an elite Demacian strike force led by Jarvan's childhood companion, Garen.
Marks: I like to get armor pent, because I want to harass my lane
Seals: Getting armor runes is a definite option, because most solo tops are AD
Glyph: I like getting AD runes, because it gives me a good harass to my oppoenents
Quints: Getting Armor runes could help you in your lane
First you would E,Q,R,W or R,W,E,Q
More magic dealers go W the shield is very helpful and it doesn't hurt to have more of a slow from the shield active. More physical damage then more points in the E for more DPS with the attack speed active/passive.
Jarvan's ultimate is a bit tricky to time and use at times. You want to avoid anyone that has a flash ability or flash of some sort, as well as people who can go through walls. So all in all Jarvan's ult is a bit useless in most cases but its good for making people waste summoner spells or catching up to people. Just be careful not to use it near a tower and having it auto queued, because sometimes it will work just outside the actual range and once your in motion its gg on your part for a free kill if your by a tower to the opposing team. Learned from experience...yup been there done that lol. If you can time your ult just right its pretty much a free kill or 2 for you team depending on how many you lock in there and the damage output of your team. Be careful not to lock your teammates in there with you as well especially squishy ones. However if you can try to use it to save teammates instead if timed correctly. This will come with practice and time so just go out there and test til you get the timing down. Otherwise stick with the saving with your slow on your W or your knock up effect combo with your Q and E.
Also as a side note do not try to use your ult on a Katarina easy shunpo and Death Lotus if you use your ult with no Magic Resist on you. Not to mention it can spell the end for your teammates that are stuck in there with you. So be careful and aware of what is the best time and place to use your ult not to mention on which champion.
Pros / Cons
Can easily escape ult with flash
Needs a lot of farming
Jarvan is great for farming. His passive gives him a little extra damage for last hitting which may or may not take some time getting used to. But it allows you to last hit with ease in most cases without getting harassed much. Otherwise his E and Q spells are great at wiping off an easy 3 minions mainly the casters once you get enough points into your abilities. Usually around 5 in Q and 2-3 in E. Otherwise just time your Q to wipe out minions in a straight line for combo gold.
Use your passive as much as you can to harass and/or harass with your Q while your farming against the opposing champion(s) to not only get gold but dish out some free damage. Also use your Standard to give site whether it be in bushes for early jungle ganking at lvl 1 or just to check the bushes since it gives site almost like a ward.
So to sum this all up Jarvan is a fun champion and a great tank/initiator that can throw out the damage. Best way I can think of him is almost like the old days of Garen. Just not as op at level 1 with the spin to win. Hope you enjoyed the guide and if I think of anything else I'll be sure to update and edit. But hope this helps those not sure of how to play the new champ and looking for some kind of guidance. Also as a side note Jarvan is good in 2v1 or mid situations since he can farm well and wipe out creep waves. Don't be afraid to try different things out either, so go out there and have fun and make Demacia proud.