Mail order box mattresses are better than I expected. Keep blankets or blinds over the windows. Keep all artificial light as low as possible. Cold rooms seem better to sleep in. Better to sleep with blankets than to sleep without anything and feel hot.
I have a secondhand mattress that rests on a set of particle board planks. Next year I'm going to upgrade to a metal frame, box, and Serta mattress
Mid-tier Ikea frame and mattress. Mixture of hard and soft pillows so I have some choice. Also recently been setting the bedroom to 18°c as apparently that helps, and it does seem to work. I do have a fairly thick duvet though.
+1 for mattress, pillows, and sheets. I don’t know how I get a good night’s sleep because I sleep through it.