Always use Deathfire Touch keystone because you dont have any use of Fervor and Warlord's keystones due to Jhins basic attack mechanics, he's attack speed is fixed and you only have 4 shots which are slowish and because of that you wont have much benefit from them plus Deathfire Touch will finish off enemies with really low HP because it deals magic damage over 4 seconds.You can swap Fury and Sorcery keystone if you want but i mostly use Sorcery due to have much impact on Jhins ulti!

Runes are really your's choice. I use standard ADC runes (attack speed, attack damage, magic resist and armor) But instead attack speed runes u can throw in attack damage runes...but small things like that are purely on you!

Try to poke champions early game and if you can use your 4th shot on champs only when you are in early laning phase. Use CAPTIVE AUDIENCE (E) often, especialy in river bush because it will give you few seconds to run away easier from enemy gank, use it under towers against enemies that can dive you (Zac, Lee Sin, Volibear etc) It will slow them and if you are quick enough you can root them with DEADLY FLOURISH (W) and do some serious damage with help of your tower.

Its really important that you position yourself with Jhin due to his immobility. If you dont you will be easy target and whole focus will be on you always. Stay behind your team within distance of your attack range. Same goes for ulti...use it carefuly and try to ult in teamfight staying behind of your team