Lux Runes explained
There's one set of runes for Lux on patch 15.4 that is the clear favorite for LoL players and pros alike. The best Lux rune paths on the position 
Support are 
Sorcery as the primary path and 
Inspiration as the secondary path with a pick rate of 36%. Besides picking runes on Lux you should learn how to play Lux and if you are interested in pro matches take a look on how a pro builds Lux. If you want to discuss 
Lux then you should visit the champion subreddit.
Lux runes from primary path
Sorcery empoweres abilities of Lux and increases the available champion resources. Most of high elo players – and our LoL pros in the the major regions – have agreed that 
Arcane Comet is the best keystone rune to run on Lux. This keystone rune adds more damage to your abilities and increases your power in the laning phase. Other primary runes on Lux are 
Manaflow Band, 
Absolute Focus and 
Scorch.
This is usually followed up by taking Manaflow Band for additional mana and mana regenaration. Absolute Focus grants additional damage while Lux is alomst full health. Scorch increases your control in the early game.
Lux runes from secondary path
When it comes to your secondary path, most Lux players prefer to go with Inspiration. Inspiration opens creative opportunities on Lux troughout the match. On the Inspiration path, the best runes for Lux are 
Cosmic Insight and 
Biscuit Delivery.
Cosmic Insight grants summoner spell and item haste. Biscuit Delivery is a great rune for laning as it gives additional health and mana, which can help in more aggressive lanes.
FAQ for Lux Runes
Which is the best keystone rune on Lux?
The best keystone rune on Lux is Arcane Comet. This Lux runes setup is then referred as Lux Arcane Comet.
What runes does Lux use?
Runes from the paths Sorcery and Inspiration are the most used runes on Lux. For the exact pick rates of Lux runes used, you have to study the rune distribution presented.