Illaoi Runes explained
There's one set of runes for Illaoi on patch
11.8
that is the clear favorite for LoL players and pros alike. The best Illaoi Runes on the position 
Top are Precision as the primary path and
Resolve as the secondary path with a pick rate of 87%. Besides runes you should take a look on Illaoi Build and if you are interested in pro matches take a look at Illaoi Probuilds. If you want to discuss
Illaoi then you should visit the champion subreddit.
Primary path on Illaoi
Precision improves attack and sustained damage on Illaoi troughout the match. Most of high elo players – and our LoL pros in the the major regions – have agreed that
Conqueror is the best keystone rune to run on
Illaoi. This keystone rune provides additional power in the later stages of a game. As soon as
Conqueror is fully charged, Illaoi deals additional damage and gains life steal. This is usually followed up by taking
Triumph,
Legend: Tenacity and
Last Stand.
Triumph restores on Illaoi a part of missing health and award bonus gold, if a champion is killed. Illaoi gains extra Tenacity with every additional stage of
Legend: Tenacity. With
Last Stand you deal more damage while you are at low health.
Secondary path on Illaoi
When it comes to your secondary path, most
Illaoi players prefer to go with
Resolve.
Resolve empowers the survivability of Illaoi and increases the tankiness. On the
Resolve path, the best runes for Illaoi are
Revitalize and
Bone Plating.
Revitalize inceases heals and shields you distribute or receive.
Bone Plating make Illaoi overall tankier, by decreasing the amount of poke damage in the early game.