Coffee Shack help needed

aloha, I have lived in Hawaii now for 10 years and have a single wall constructed home in Makakilo. I'm looking for someone who can renovate the home room by room over the years. Any suggestions? I'm focusing on thickening up the walls so sounds do not transfer from bedroom to bedroom to bedroom. should studs be added to the single walls filled with fiberglass insulation and covered with drywall or would it work just as well to apply the drywall directly to the walls and then add another layer of drywall over that? I'm looking for someone who is familiar with upgrading these homes.
also, I am a blind senior citizen on a fixed income and can only do a couple thousand dollars worth per year. Any suggestions would be greatly appreciated!