The Foestriker set from the first 2-3 dungeons and/or the "Brand New War" set acquired from the Hall of Novice. They are the same set in different colors. Honestly I feel making the Brand New War set dyeable would be better. You receive it at level 15 which is also when the dye system unlock quest becomes available.

I'd also like to see the Lakeland Aiming set become dyeable. The models for this entire set already exist in dyeable form as the "Facet (Coat, etc) of Crafting" set for Disciple of The Hand.