I'm thinking that Luka would be wearing some kind of street wear since she could be the ruler of a gang who fights to take over territories.

Mizu I would imagine would walk around in a pretty skirt and be overall lightly clothed when she's not doing any kind of jobs.

Beraga may be a character I haven't drawn that often since he's not a major character in the book, but I still felt like drawing him. So he's gonna wear a stylish suit because he's a knight, a magic knight at that, making him a noble, meaning that he should wear stylish clothes like these!