Essentially, all costume without attributes are very cheap and can be purchased directly. The only valuable costume is the Stalker costume in the mall (can be enhanced by the Blacksmith Wu), which can be upgraded to CandeDragon[Black]. The top-tier costume is Frost Shine, with the following attributes:
Costume Enhance
The Stalker costume and CandeDragon[Black] can be enhanced at the Blacksmith Wu using enhancement materials (either Costume debris or Stalker costume can be used as materials). It is roughly estimated that enhancing a few Stalker costume will be sufficient to reach the maximum level.
Costume Upgrade
At the maximum level, the Stalker Costume and CandeDragon[Black] can be upgraded at the Blacksmith Wu NPC for Costume Enhance
Stalker Costume[Full] + Combine god bead = CandeDragon[Black]
CandeDragon[Black][Full] + Dust Beads = Frost Shine
Costume Convert
CandleDragon[Black], Frost Shine can be used at the NPC Agent Shang to convert the appearance of costume. Each conversion requires the consumption of 99 Advanced stone.
PS: Each conversion has a chance of failure.