Ruby's clothes: A more form fitting uniform to fit her role better in combat. Not as intrusive and is comfortable
Weiss's clothes: Adds a level of maturity showing how she has grown mentally.

Yang's clothes: Similar to Weiss it shows a change in personality and maturity. It is similar to how a Rape Victim may use less reveling clothing in their everyday life as a way to move past the trauma

Blake's clothing: The same concept as the three previous except where as Yang is subconsciously hiding, Blake is accepting who and what she is.

Nora's Clothing: Shows a change in her base personality, instead of being the crazed fighting girl she was before she is instead more responsible and acts as the Hawkeye of the group.

Ren's clothing: Shows a subtle drive to be more involved in keeping those close to him safe. Subconsciously trying to be intimidating to ward off any potential threats.

Jaune's clothing: Shows a change in key personality traits. More armor means that he plans to be the tank of his group. Better supplies shows that he is taking his responsibility of leadership to the next level. The additional gold trim and red fabric is a symbolic gesture to his late partner and as a sign of fortitude to hold true to his unsaid promise. (Similar to how Aragon wore the the gauntlets of Boromir after he died.)

Ayyy, love the punchline in the end.