My lounge and my sleepwear capsules overlap. (I love items that can be worn in more than one way. I don't buy sleepwear that screams "sleepwear," as I actually want to be able to use it in public, too--at least in summer--and styled with other items.) My lounge capsule includes:
● 2 pairs of (very moderate) harem pants: 1 plum with white polkadots, 1 navy & white "ceramic" patterned.
● 1 pair loose deep green velour pants.
● Several long t-shirts (and for summer, also a few long singlets), also used as nightwear. One is floral, others have hearts or polkadots prints and some have Breton stripes, are graphic or have splashes of various colours. I will also use regular solid tees and tank tops in various colours.
● If I need a topper, I will often use a long cardigan or a long open button-front shirt. And if I need some warmth against my neck, I will wear a big, soft scarf.
● I will also wear cotton or light wool socks, depending on the season. And Birkenstock style sandals.
HOWEVER, none of my capsules are very strict, as I love to mix things up a bit and play around with my clothes, footwear and accessories. So instead of a long tee, I might wear a short velvet tee or a longsleeved crewneck pullover from my regular wardrobe. And I might wear ballet flats and add a bracelet or a short necklace. Often, I will also wear an item like jeans, loose pants, a skirt, dress or button-front shirt as loungewear--it just needs to be soft, comfortable and practical.