Build Guide by
Not Updated For Current Season
Jarv is obviously dps. Whether his recc build says so or not. He can single out and ***punch one or even multiple ppl. I feel he's a great support as well as putting out massive burst dmg himself. Pairing him with someone that can dash into the fight (and better yet his ulti) such as xin or akali.
For SummonerSpells===I found flash exhaust to be the best choices. You don't really need ghost walk since you have a long range pop-up using flash can instantly put you in the right position to Q+E. And exhaust, you trap your opponent in your ulti and its a duel, so you exhaust him and your BC is reducing his armor along with his dragon strike. Nuff said.
First off BlackCleaver. (Boots, I've been getting attack speed boots to maximize burst dmg) Back to BC; You get your target trapped in your ulti and you beat his ***. Reducing armor with BC and your dragon strike is devastating even to those with a lot of life.
Madreds Bloodrazor is great if they have lots of fatties but I feel that Jarv is too burst dmg to put it in his normal build.
After BC, go for more attack speed and life steal. Starks works wonders. Bloodthirster for more nuke damage or Wrigglers Lantern if theres a fed dps to counter.
To counter a fed dps, as I said lantern is great, and if their dps is really a big problem i recommend stacking life and grabbing an AtmasImpaler for extra armor and much needed dmg since you'll be sacrificing more dmg output.
You NEED a life item unless you get horribly fed. I've found it easy to get trapped in your ulti and your Q+E combo is on CD you can easily seal your fate. So Frozen Mallet is good but if your opponents are getting fed quickly then get Warmogs which will in turn help your AtmasImpaler that much more.