If you´re playing her top, here's the tip any sane Kayle main/OTP will give you: Stop.
Play her mid instead.
Ban Anivia/LeBlanc/Ahri, hope they don´t pick Azir/Aurelion Sol. If they pick something like Katarina, go Exhaust, everything else either TP or Ignite.
Lethal Tempo for keystone
Triumph/Presence of Mind
Legend: Alacrity
Coup de Grace/Last Stand
Transcendence
Gathering Storm
as core. You can go for Zerker's instead, but i still like capping CDR on her. 54 seconds worth of ult CD is amazing.
Wit's End before or after Guinsoo's, if you´re against a lot of magic users. But after those four items, you can choose if you want to continue with the on-hit build with BORK and Runaan's, or go a more AP heavy route with Void Staff and Rabadon's.
She's decent in Season 8. All you gotta do is hope your team doesn´t shit the bed until you get your core items. But even more important, make sure not to shit the bed yourself, or if you do, hope the enemy team throws enough for you to make a comeback.