Trundle Runes explained
There's one set of runes for Trundle on patch
12.12
that is the clear favorite for LoL players and pros alike. The best Trundle Runes on the position 
Jungle are Precision as the primary path and
Inspiration as the secondary path with a pick rate of 60%. Besides runes you should take a look on Trundle Build and if you are interested in pro matches take a look at Trundle Probuilds.
Primary runes path on Trundle
Precision improves attack and sustained damage on Trundle troughout the match. Most of high elo players – and our LoL pros in the the major regions – have agreed that
Press the Attack is the best keystone rune to run on
Trundle. Trundle has a very easy time activating this rune with basic attacks which synergises well with
Press the Attack’s damage increase once activated. Other primary runes on Trundle are
Triumph,
Legend: Alacrity and
Coup de Grace.
Triumph restores on Trundle a part of missing health and award bonus gold, if a champion is killed.
Legend: Alacrity grants additional attack speed to Trundle. Trundle deals with
Coup de Grace more damage to targets with low health.
Secondary runes path on Trundle
When it comes to your secondary path, most
Trundle players prefer to go with
Inspiration.
Inspiration opens creative opportunities on Trundle troughout the match. On the
Inspiration path, the best runes for Trundle are
Magical Footwear and
Cosmic Insight.
Magical Footwear allows Trundle to focus on those essential core items without the need to spend the additional 300 gold on boots.
Cosmic Insight grants summoner spell and item haste.
FAQ for Trundle Runes
Which is the best keystone rune on Trundle?
The best keystone rune on Trundle is
Press the Attack. This Trundle runes setup is then referred as Trundle Press the Attack.