Blankets. Blankets are all that are required.
Naked Apron or Handbra Jeans depending on the time of day
Properly worn without underwear.
What about just shirts?
White oxford on top, bottoms are optional.
But... but this just makes the girl look slutty as if she's ready for sex
Winter outfits. Bonus points for えんぺら
That's boring. Some clothing helps with a sense of imagination, a sense of wonder. Seeing a girl in a skirt and hoping for a sneak of her panties is special. Even just the wondering of what kind of panties she is wearing is special.
No clothing takes all of that away.