Maokai Runes explained
There's one set of runes for Maokai on patch 15.14 that is the clear favorite for LoL players and pros alike. The best Maokai rune paths on the position 
Support are 
Resolve as the primary path and 
Inspiration as the secondary path with a pick rate of 75%. Besides picking runes on Maokai you should learn how to play Maokai and if you are interested in pro matches take a look on how a pro builds Maokai. If you want to discuss 
Maokai then you should visit the champion subreddit.
Maokai runes from primary path
Resolve empowers the survivability of Maokai and increases the tankiness. Most of high elo players – and our LoL pros in the the major regions – have agreed that Aftershock is the best keystone rune to run on Maokai. This keystone rune bulks you up, increasing both armour and magic resistance, once you immobilized a champion. Aftershock synergises both with the sheer amount of crowd control Maokai possesses and the need to be tanky as soon as you engage. Other primary runes on Maokai are Font of Life, Bone Plating and Unflinching.
Font of Life provides your teammates with more sustain by healing them whenever they attack a champion whose movement you've recently impaired. Bone Plating make Maokai overall tankier, by decreasing the amount of poke damage in the early game. Unflinching inceases Maokai tenacity based on your missing health.
Maokai runes from secondary path
When it comes to your secondary path, most Maokai players prefer to go with Inspiration. Inspiration opens creative opportunities on Maokai troughout the match. On the Inspiration path, the best runes for Maokai are 
Cosmic Insight and 
Hextech Flashtraption.
Cosmic Insight grants summoner spell and item haste. Having an extra way to decrease the distance with the Hextech Flashtraption will make an engage much easier to pull off.
FAQ for Maokai Runes
Which is the best keystone rune on Maokai?
The best keystone rune on Maokai is Aftershock. This Maokai runes setup is then referred as Maokai Aftershock.
What runes does Maokai use?
Runes from the paths Resolve and Inspiration are the most used runes on Maokai. For the exact pick rates of Maokai runes used, you have to study the rune distribution presented.