Bass wood is the easiest to work with and readily available at any store that sells craft wood. It is a bit of work to finish if you are staining or painting. There is no real grain on it either, so it stays to scale. Are you asking about the rooms walls? Or the appliances? Really any wood you like, as long as the grain is small and will look good going 'small'.
It's going to be 2 walls and a floor... so it can look like a display.
is this a miniature to be played with? or for display? balsa wood is very light and easy to work with, but doesn't fair well being played with.
pine can be sturdier and played with.
It's going to be for play. I'll be miniature cooking with it.
Bass or Balsa wood.