Building a homewear wardrobe from scratch
Most people's homewear situation is a collection of things that accumulated over time: an old T-shirt, a pair of joggers from a gym phase, a robe that was a gift several years ago. Building a deliberate homewear wardrobe from scratch is a different exercise, and it does not require spending a lot at once.
Start with one good sleep set
The first thing to get right is what you sleep in. A washed cotton sleep shirt or a two-piece pyjama set in satin or modal will serve you better than a collection of mismatched pieces. Choose based on how warm you sleep: if you tend to be warm at night, a sleep shirt in washed cotton is the most versatile option. If you tend to be cold, a two-piece in a slightly heavier fabric gives you more coverage.
One good sleep set, washed regularly, will last a long time. There is no need to own several before you know what you like.
Add a robe next
A robe is the second most useful piece in a homewear wardrobe. It extends the usefulness of whatever you sleep in by giving you a layer for the morning and evening hours when you are not quite ready to get dressed. A waffle-knit cotton robe is the most versatile choice: it is not too warm for mild weather and not too light for cold mornings.
The mistake most people make with robes is buying one that is too short. A robe that falls to the knee is less useful than one that falls to the mid-calf, because the longer length works over more situations.
Lounge sets come third
A lounge set is the piece you reach for when you are spending a full day at home. It is distinct from a sleep set in that it is designed for sitting, moving around, and occasionally being seen in. A brushed French terry set or a ribbed modal two-piece works well here.
You probably only need one or two lounge sets. More than that they start to feel like a uniform rather than a wardrobe.
The whole wardrobe can be built over a few seasons. There is no rush, and buying one good piece at a time is a better approach than buying several mediocre ones at once.