He's not strong right now.
You need to comet as a rune to do any real damage. The precision tree just isn't great for him as a primary tree.
Jhin pairs best with supports that are hard engage (his W prevents escapes), high damage (his execute damage likes lower health targets), or ones that allow him to trade with his 4th shot (but not against a fleet-footwork adc)
I believe the new rune they're adding to the precision tree is going to help Jhin.
Also, if you're just learning- Jhin needs to kite. He actually has to kite other adcs. If you can trade one auto for one auto vs another adc, you'll win. Stand there autoing them at full health and you'll have problems if you're not fed.