You can also go Biscuit Delivery and Cosmic Insight if you prefer. Both options feel fine to me. For the stat slots, Adaptive stats and Armor are always solid. I usually go for something like AP/AP/Armor or AP/Armor/HP.
With all due respect, there are plenty of guides out there that'll tell you what runes work well for Rakan. All it takes is spending some time to read them.
Comment has been deleted