Sett Runes explained
There's one set of runes for Sett on patch 15.14 that is the clear favorite for LoL players and pros alike. The best Sett rune paths on the position 
Top are 
Precision as the primary path and 
Resolve as the secondary path with a pick rate of 88%. Besides picking runes on Sett you should learn how to play Sett and if you are interested in pro matches take a look on how a pro builds Sett. If you want to discuss 
Sett then you should visit the champion subreddit.
Sett runes from primary path
Precision improves attack and sustained damage on Sett 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 Sett. This keystone rune provides additional power in the later stages of a game. As soon as Conqueror is fully charged, Sett deals additional damage and gains life steal. Other primary runes on Sett are Triumph, Legend: Alacrity and Last Stand.
Triumph restores on Sett a part of missing health and award bonus gold, if a champion is killed. Legend: Alacrity grants additional attack speed to Sett. With Last Stand you deal more damage while you are at low health.
Sett runes from secondary path
When it comes to your secondary path, most Sett players prefer to go with Resolve. Resolve empowers the survivability of Sett and increases the tankiness. On the Resolve path, the best runes for Sett are 
Second Wind and 
Shield Bash.
Second Wind powers up your sustainablity in lane by healing after taking damage from an enemy champion. Shield Bash powers up your tankiness and empowers your next basic attack while you have a shield.
FAQ for Sett Runes
Which is the best keystone rune on Sett?
The best keystone rune on Sett is Conqueror. This Sett runes setup is then referred as Sett Conqueror.
What runes does Sett use?
Runes from the paths Precision and Resolve are the most used runes on Sett. For the exact pick rates of Sett runes used, you have to study the rune distribution presented.