Farm at 16 as much as you can. If you don't have the patience to farm everything there, farm again at either:
52 the penons
64 PEG's
72 nachals in garments
The build is strong.
As for the skills, you might want to go bicheon/fire/light/ice OR: bicheon/heuksal/ice/light OR bicheon/heuksal/fire/light.
All are good alternatives. It's up to you what you do.