This is a guide for everyone wanting to learn and improve his skills on Jhin. I have been playing him non-stop since his release and I think he can be the most fun adc in the game (>200 won ranked games in season 6 and ~100 games season 7 to this point).
At the moment Jhin may have problems because of his lack of mobility and the amount of asassins in the game ( he has a very low winrate) but with this guide I´m sure you´ll make it through any elo. Anyways lets get ready to Rumble.

+ Long ranged
+ High damage
+ Probably the best ult to make yourself usefull in teamfights when lowlife
+ Best lore in the game
+ Best lategame AD scaling there is

- Needs a LOT of Peel
- Weak when behind
- High skill cap
- positioning is his key (hard to master)
- Lack of mobility and real cc
- skillshots (duh...)

First of all lets start with the things OUTSIDE of the game. Lets start with the runesFor runes I go with flat AD Quints since Crit doesnt do anything until late game where Jhin is already a beast. You need help in early, thats why I took flat AD. for Seals and Glyphs I took Armor and Magic resist as with most champions. For marks I took Lethality because this gives exactly 14.4 lethality, which to me is the sweet spot against any other ADC without trading too much AD out of your runes.
For the real advanced one here: You can also go Lethality Quints and Marks granting you no AD but 24 lethality on Minute 1 making even his armorpen build as good as the crit build in lategame.

For Masteries I go 18/12/0 but 12/18/0 can be considered too but in my opinion its way too hard to trigger Thunderlords. Also Warlords is scaling well in every aspect of Jhins passive and playstile. Espacially since it scales from AD, not dage done. Jhins AD tends to be high. Else I take dangerous game for obvious reasons as well as merciless, because you don´t need the extra mana and it increases the crit damage because you usually use your 4th shot on low HP opponents.

There are a lot of crit Jhins but after a lot of testing my opinion is to go hardcore ad. Youmuu's Ghostblade is your first item. Good AD, armor pen and the speed helps escaping and engaging. And don´t forget apeed gives you more AD ;D.
Second, go Infinity Edge, which gives good AD as well as more power to your crits. This item is really good on Jhin because most ADC´s cant work with the 20% crit but Jhin crits every 4 autoattacks anyways so it´s a blessing to get more crit damage. 3rd go rapidfire canon, which gives you the 50% crit chance total and the sexy range you need. Also 5% movement speed is always welcome on Jhin. After thsi (the core) go Essence Reaver for a good AD portion and 70% crit chance added to never ending mana, especially in poke heavy teamfights. Boots should be boots of agility because Jhin doesn´t scale well on berserkers greaves and essence reaver + yomuus already give you 40% cd.
To finish your build go either Bloodthirster for sustain, Guardian Angel if the enemies have burst, mercurical scimitar for anti cc + lifesteal, or Last Whisper against high armor enemies.

Max Q first. This ability works as a second autoattack and works wonders between autoattacks and reloads. Also using Q to kill all 3 caster/ melee minions + a hit on the enemy is a wonderfull combo and usually makes you having the high ground for a short period of time.
Max W second as it´s cc and scaling increases drastically. Sometimes you can skill this first in case of invade or second brush assassination. But I usually go Q on lvl 1. On lvl 13 you can then skill your E. I don´t really like this spell although it has a very good AD scaling. Some level it earlier for better escape but I don´t really feel the need for it so I pick it up only if it´s necessary.

For spells Flash is a must have because Jhin lacks mobility. Second you should take Heal to get yourself out of sticky situations but Barrier and Ignite can be considered, especially in the mid lane because barrier may save you from ap carries.

Jhin works very well with poke/ damage supports. These would be Zyra, Morgana and Lux, Brand. But Sona is quite **** with Jhin because he can´t quite follow without risking to still kinda loose the trade. The trick is to keep the enemies low HP so you crits do even MORE damage due to the missing HP scaling. Also the top mentions I wrote above have some sort of cc, which is wondefull to time your W into to increase the cc and damage done. Witht these supports Jhin works like a lane bully even in early game. But with defensive champs like Braumand Janna Jhin also exels, but not in early. In mid to late game though he has enough defense to stand there like a turret and smash anyone on his way.

Caitlyn and Draven are your nightmares. Dravens autoattacks smash you and his movement speed bonus lets him follow up with more if he gets near you. Just stay away and hope your team cc´s him for you to hit him. Caitlyn just has high range and some cc to keep you in her range. The problem with her is that she also scales very well into late leaving you dying in 1v1´s ( which happens with most others too but with her its worse). Ashe also is quite dangerous. But so are many ADC´s because they can survive on their own and Jhin is more of a utility ADC making him better in teamfights but very bad in splitpushing.

Jhin is a hyper carry. Not because of his items but more because of his scaling. It is not uncommon to have 700 AD in late game. You should spend most of your time farming the lane. But don´t push it too deep, since you have nearly no escape. Helldrakes are a must for you since the extra percentage is a holy gift for Jhin. edit: I know farming may be hard because of the low Attackspeed and only 4 bullets but it will come naturally, so one day you will farm with him just like on any other champ.

I´ll consider mid-game as the phase in which the teams start little teamfights and people start running around everywhere. Your goal is to NOT BE ALONE because you have no escape. Although you need to farm you are not a splitpusher. Keep that in mind. In teamfights hit the carries of course but don´t go too close or you might no come back. Try to youse your 4th autoattack on low-life targets for obvious reasons.
The one good thing Jhin has is that unlike on other ADC´s it is ok for Jhin to hit a tank in a teamfight although he might be able to hit someone else, because his crits shred tanks in short time. After reload you can resume to killing ADC´s and mid laners. And because of the crit movement speed, repositioning is quite easy.

Given that you reached the late Game you have a lot of jobs in a teamfight. First of all you should set traps everywhere where your team can catch up on a slowed enemy. A trap in the enemy team is useless since they will walk out of it and even if you snare one that wouldn´t be enough for an engage. You should see the traps as an escape way in lane and in teamfights. I a enemy is leaving his team for a poke ability snare him and let your team do the rest. If the enemys run or you are on 10HP ult them. Since it slows you shouldnßt always go for YOUR kills but maybe cc the enemy cowards. As already said Jhin needs peel and placement is your first and most important rule.
Your damage is crucial to the fight. Hit your first 3 shots on squishies but the last shot on half life tanks. This will guarantee you good damage output. And always rather run than go risky because you team needs your 4 auto attacks. Rather on the enemy tank than dead trying to hit a Zed or whatever.

I hope this guide helped you to understand Jhin and his playstyle. Please rate this guide and don´t mind giving crtitique since my aim is to get better at making guides.
Here´s a video you can have fun with. It´s not mine but it´s my favourite
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