This comp uses a lot of powerful late game units to create a strong high cost team. Kayn is the focal carry with damage items, but there are a variety of units you can itemize depending on who you find Chosen.
This comp shouldn't be something forced. You can pivot into this comp late game if you have no clear direction with your items or find Kayn 2 very early.
Level up to 4 early if you want to start a win streak. Level up to 5 to try and continue the streak.
If you're weak in the early game, you can opt to save gold and lose streak
At Round 2, level up to 6 regardless of your start. Put together the strongest team you can.
At Round 1, level up to 7. Roll down to stabilize your comp if you are weak. Afterward, save up to hit level 8 and complete your comp.
The comp doesn't require a Chosen, so you should build your 8 or 9 unit comp around whatever Chosen you find.