Senna Runes explained
There's one set of runes for Senna on patch 15.14 that is the clear favorite for LoL players and pros alike. The best Senna rune paths on the position 
Adc are 
Precision as the primary path and 
Inspiration as the secondary path with a pick rate of 65%. Besides picking runes on Senna you should learn how to play Senna and if you are interested in pro matches take a look on how a pro builds Senna. If you want to discuss 
Senna then you should visit the champion subreddit.
Senna runes from primary path
Precision improves attack and sustained damage on Senna troughout the match. Most of high elo players – and our LoL pros in the the major regions – have agreed that 
Fleet Footwork is the best keystone rune to run on Senna. This keystone rune generates you a lot of sustain and increases your survivability against poke champions in lane. Other primary runes on Senna are 
Presence of Mind, 
Legend: Alacrity and 
Cut Down.
Presence of Mind helps Senna with the mana problems by restoring missing mana, if a champion is killed. Legend: Alacrity grants additional attack speed to Senna. If the enemy team consists of multiple tanks, then the rune Cut Down is the best choice.
Senna runes from secondary path
When it comes to your secondary path, most Senna players prefer to go with Inspiration. Inspiration opens creative opportunities on Senna troughout the match. On the Inspiration path, the best runes for Senna are Approach Velocity and Biscuit Delivery.
Senna gains bonus movement speed by Approach Velocity, while moving toward enemy champions that are immobilized or slowed. This rune is perfect to follow up engages by your teammates. Biscuit Delivery is a great rune for laning as it gives additional health and mana, which can help in more aggressive lanes.
FAQ for Senna Runes
Which is the best keystone rune on Senna?
The best keystone rune on Senna is Fleet Footwork. This Senna runes setup is then referred as Senna Fleet Footwork.
What runes does Senna use?
Runes from the paths Precision and Inspiration are the most used runes on Senna. For the exact pick rates of Senna runes used, you have to study the rune distribution presented.