In summer, absolute minimal. Fitted sheet, pillows,and either sheet/empty duvet cover, thin duvet in cover etc depend on the temperature.
in winter, similar options really as I get hot at night. At the moment I have a sheet with an empty teddy bear duvet cover, it's about right for me. I do have the duvet with another cover on, folded up in a chair in case I get cold.
plus I have A gorgeous winter cushion that leans on the pillows. That & the teddy bear duvet cover make the room look cisy without a ton of faff!
if I wasn't singularly heating the planet I'd just have the duvet under the teddy fleece cover.
in between seasons I do sometimes have a throw across the bottom of the bed which I like the look of, but it's practical as well
as ornamental.
I feel like I've got the maximum 'cosy look' with the absolute minimal fuss.
I'm too lazy to fuss about with things that are purely 'dress'. I've been through phases of 'lots of cushions' &/or several layered throws. But although it looks nice once done, they mostly ended up on the floor or on the chair.
IF you do something purely decorative, accept DH WILL JUST push them
off at night & don't expect him to faff about making it look 'just so' in the morning. You want the faff, you take responsibility for it 😁
& post us a picture!