Not asking for something very loud and gaudy, but yes, definitely the Creatives of the show need to change Riya's wardrobe.
It's always been at the back of my mind that Rani wears very pretty sarees in comparison to Riya. Creatives must be trying to show that Riya values money hence she does not spend on unnecessary clothing, whereas Rani is slightly immature and goes beyond what's affordable to her. She is always shown going to the market for shopping (which Riya never does).
I like your idea of night dresses. A little bit of creativity will not do any harm.
As for Rani always having money and Shivam having none - let's not try to use logic for this show. There's just too many bloopers.