I’ve been working on doing this too!
Here’s what I’ve done so far:
Everlane sleep shirt
Silk nightie (similar)
Short sleeve PJ set similar
I also have a tank and boxer set from the gap.
Depending on the weather and my mood, I switch these up. When I get out of bed, I put on either a large/warm robe that looks classy, a silk kimono or a to the ground cozy cardigan. These make loungewear feel as comfortable as your favorite sweatshirt and can really elevate the look.
The thing I most want to add is a long sleeve and pants set and I’m thinking about silk feeling material. Tried on this the other day.