This is basically a quick guide outlining the items I use when playing dominion. This isnt a fancy pants awesomely highly detailed guide, just a small outlook on what I use. I am not interested in putting hours on end to complete this fully, but instead just help people find their own way. Im not a top elite player or master at this game, so dont rely on this guide to be the best possible one out there. BUT, since Ive been using this item build, Ive been coming in first 60-70% of the time, with the added in few stupid matches everyone gets mixed up into (useless teammates, getting just plain unlucky.. etc.)
This guide has no pictures too, so ITS SERIOUS.

I always buy level one boots and prospectors blade at the start for the perfect balance of mobility and damage. I almost never take bottom or mid, Jarvan isnt fit for taking mid and I like to go top instead of bottom (personal preferance). I always get the speed buff as I run up top and try to interupt the enemy from caping with a quick knockup (Flag+dragon strike combo), I then hit as many people as I can at least once to bestow my passive upon them. I then run back a bit and let my teammates get some hits in. Than I run back into the battle and give it everything I got. If things are getting a bit sketchy, you can flash out and get the health above or just plain run away. If they got windmill, try and defend your mid as much as possible from aggressive enemies, and proceed through the match trying to get back windmill. If you have the windmill be ready to defend it with your life, its a valuable point.

Building Demacian Standard is one of your first priorities. It both helps your teammates and gives you a double buff. Right at the start of the match I put 2 rankes into Demacian standard and 1 rank into Dragon Strike. Than one rank into Golden Aegis just for its slowing ability. Proceeding through the game, I build Demacian Standard to its fullest, providing my surrounding teammates (and myself) with upgraded stats. After I max out DS, I proceed onto maxing out Dragon Strike to increase my damage output as much as I possibley can (along with a rank in Golden Aegis just in case). As you max your abilities out, always upgrade your ultimate whenever possible (lvl 6,11 16).

Jarvans ultimate can be extremely useful in a 1v1 fight, or helping a fellow champion. If I happen to get into a 1v1 fight with someone and I need that extra amount of damage I will pop my ult. It seems like a waste but it isnt. I will only use his ult if its a forsure kill though. For example, I see one person trying to cap the storm shield buff. I will pop my flag onto them and hit them up into the air with dragon strike, than proceed whacking them with basic attacks ( passive helps a lot). I see that my ults ready, so I keep attacking him until we both get down to about a third of our health. I will than pop my ultimate and hit them a few times to finish them off. people dont expect this. They dont expect DEMACIAAA, followed by a huge chunk of their health being ripped off.
Jarvans Ultimate can also be used to trap a single person in your entire teams kill radius.

I just cant stress enough how effective his Ultimate is. Say me and my teammate see sion hugging a turret. Me, Jarvan the initiator he is, will pop my flag and hit him up with dragon strike. I than pop my ultimate to prevent him from kiting and use golden aegis to absorb a tower shot or two. If I somehow dont kill him, I'll pop flash and get outttttta there. If i didnt egt him, my teammate sure will. I know this is VERY general, but just bear with me, im just describing a few strategies here.

Windmill(top tower) is where Jarvan shines. I usually hide up top in the bushes above the tower and wait for a unsuspecting enemy. As soon as one person tries to come and cap the turret, I'll come running out, throwing my flag and knocking him/her up. If done right the tower will also hit the enemy champion once or twice. This is extremely effective early game. Just be wary of multiple champions approaching. Two enemy champions and you still have a chance, 3 defend with your life, 4 recall or just get outta there with ghost.
Note: ^--- This can be used at other towers, but is a bit more tricky.

-He is extremely effective at stopping enemy champions from capping points.

-He can defend and kite very well.

-You can save teammates and feel like a hero.

-He can take a bunch of damage while dealing a decent amount at the same time.

-He can escape a gank easily with the power of flag jumping+ghost+flash.

-He is just a all around good character for everything.

-His passive is ridiculous.

-"DEMACIAAAAAAA" - Jarvan himself

For just a quick note on summoner spells, use what your comfortable with. If you've been using ignite and exhaust your entire play history THEN USE THEM. You know how to use them and thats all that matters. I personally use flash and ghost because of the mobility, and dominion is all about mobility.

Flash:

I use this spell ALWAYS. It is extremely useful for getting out of battle quick and easy, and not mentioning ganks also. If you initiate a fight and get low on health somewhere down the line, just flash out of the battle and let your teammates take down the enemy champions trying to get that last hit on you.

Ignite:

Can be very useful, a flag knockup+catalclysm+ ingite will surely put a big notch in there health bar.

Exhaust:

This can be used to get a advantage in a fight or for simply making a getaway. self explanatory.

Ghost:

Useful for catching a enemy or running away from a enemy. When your making a getaway, try and hit the closest speed buff for a giant speed advantage.

Revive:

Just please no, its a terrible spell to be using in dominion. It has a 10 minute cooldown, and games usually last only 15-20 min.

Every other spell I havnt really used enough to give you any specific advise, so thats why im going to refer to my above statement and say, use whatever you think your best with. (I strongly advise flash though XD)

This item build I've shown you guys is what Ive been using since I started dominion, and I've been dominating with it. The trinity force build never fails. Whatever you do DO NOT buy gold per 5 second items, the game is too short and you get enough moneys anyway. I usually build attack at the start (Phage) at the cost of mobility, but I buy boots right after. Building attack at the start will give you a big advantage over other enemy champions. Jarvans naturally built attributes and in combination with runes will provide you with your defense at the start. I build defense later in the game to make up for my pure dps start. Atmas impaler with sunfire cape is a very wise choice. They will provide a strong amount of health, armor, crit chance, and more attack! The last item is all up to you. Dominion games usually do not last long enough for you to build your last item, but a good choice would be Youmuus Ghostblade for that extra kick of damage, or Randuin's Omen if you feel a bit squishy. Any item with Health regen is a meh, just pick up the health buffs around the map whenever possible. If your last item is a defensive one (other than Randuin's Omen), it should be built to compensate for the enemy teams main type of attack (magic or melee resistance).

Jarvan IV is well known for his ability to stop people in their tracks and single people out. Jarvans knockup ability is so versitile , I cant even begin to describe it. It knocks people out of combat for a few seconds, stops them in their tracks, can do A LOT of damage, and lets your teammates beat the living hell out of them long enough to give that extra advantage.

Onto another point, if you saw someone being chased by a enemy champion through the forest and your close by, go save them! Its a good chance that the enemy has already been partially weakened already, so this your moment to be a hero. Rush in, pop your flag, knock them up, and use Golden aegis. This will hit them up into the air for a second or two and slow them by 20% for a few seconds also. You can also most likely get the kill too :D! If theres more than one champ, than just run as soon as you use your shield, and flash if necessary.

Onto another point, keep scanning your map as much as you possibley can. If you and two other teammates are defending top, and bottom is getting ganked by 4 people, recall and run over there as fast as possible! Trust me, your teammates will love you.

Onto another point, If you see theres three of you trying to cap top, when there four people defending, run over to their mid tower and start to cap it. You may only get it to neutral if your lucky, but it sure will panic the other team and break them up enough for you guys to cap it. As soon as you see a enemy running towards you, run. Its most likely there'll be more on the way.

I just cant stress enough, keep checking your map, keep tabs on where your enemies are and how your teammates are doing.

I just wanted to throw this guide out there to show you guys how I play, and how I dominate in Dominion. This guide is a bit unorganised I know, but it is just a few techniques I have jumbled together for you guys to critisize and love. I bid you farewell and good luck in dominion.