Never been to Russia, been pretty close to the border though.
Depends what kind of dress you’re going for! If I’m looking for a nice, casual everyday kind of dress that I can wear either to work or just to hang out with friends, then your standard H&M or Primark type chain shops absolutely do the trick (one of my favourites here in Norway is called Lindex). If I’m looking for something nicer, the absolute best is to go to those shops that have both second hand/vintage and newer things in the same kind of style(s). You know, the shops that have lots of pin-up clothing but also stuff for normal human beings.
I don’t buy dresses online because I have a hard enough time finding a good fit irl due to the combination of my height and body shape. Wish I could, there’s so much amazing stuff out there.