Druid Robe (F) is crafted with Tailoring in Mabinogi (robe). This page lists everything needed to make it, checked against the game as it exists today. The interactive planner lives in the Tailoring Companion.
How to get the sewing pattern
The sewing pattern is rank 3 and survives 30 uses; every crafting attempt spends one use.
The New King's Request (Hard): Clear the Hard difficulty of The New King's Request theater mission.. Party of 1 to 3; requires The New King's Request Pass for Hard difficulty.
Materials
Expect about 7 attempts per finished item (15% average progress per attempt). Per-attempt materials are consumed on every attempt; finishing materials once per item.
Each attempt uses
3× Finest Silk — weaving on a loom, higher rank
2× Finest Fabric — weaving on a loom, higher rank
5× Tough Thread — weaving Thin Thread Balls
Finishing (once per item)
1× Finest Finishing Thread — Buy directly from any general goods NPC shop.