Hello, I am summoner CheesyBoy8 and I have some experience on Jhin and how he works.

Arcane comet offers lots of damage when going for trades in lane with your fourth-shot and it also gives more damage when using your W and ultimate. Nimbus cloak is useful if you don't kill someone with your ultimate and you can get in range for a W or Auto-attack. Because you can stand so far back and deal so much damage, it is unlikely someone will reach the backline and deal damage to you so Absolute Focus is a great rune to take. Gathering Storm is taken on every ADC to give extra late-game power. Overheal and Coup de Grace are for in lane situations.

My Jhin build is a mixture of AP (to deal extra damge on Q, W and E) and AD. This means it is hard to build against you.
Jhin build:
Stormrazor
Duskblade
Youmuu's
Banshee's Veil
Zhonya's Hourglass
with Ionian Boots of Lucidity.
By the time you have completed your Youmuu's, the enemy will have stacked armour so you can deal more damage to them with the AP.

Flash and Teleport is freat on Jhin as it offers up the possibility of roams later on in the game with Teleport and flash offers escape because of your relatively low mobility.

Max Q, then W, then E as this offers the most damage and waveclear then you will get along with the opportunity to four-shot a squishy.

Overall Jhin is a good champion to pick up and learn for the good matchups he can play in. I wouldn't say that maining Jhin is bad, but he doesn't offer much to his teammates and severely lacks any good mobility.