For me it was "buy high quality pillow" because you sleep for one thrid of a day etc. I needed a new pillow anyway so I came to the store and bought the best they had. And it was ... ok. Like it's a fine pillow but my sleeping haven't improved really, it's basically the same. So I was disapointed :(
Just to respond to your need for better sleep... For me, good sleep is far more about temperature, darkness, and a nice weight. So I use a weighted blanket, eye covers, and the expensive but awesome chilipad so I don't try to sleep in a pool of sweat.
Same for me, minus the weight. I hate weight on me when I'm sleeping. Makes me feel trapped and claustrophobic. I use the thinnest blanket the temperature will allow, and I always have fans (and if possible an AC) going. Anything above 63f/17c and I sweat like a pig. :(
I've been using it for roughly 5 years so it's probably an old version but it does exactly what it says it does. Ie. It's a water regulated mattress pad with a thermostat so it stays at whatever temperature you set. I have to clean it out now and then with hydrogen peroxide and add water every month or so. The heater stopped working at some point a few years ago, but I never need heat anyway and the cooling system works fine. I also set the cooling system well above my bed and that helps the circulation. But it was like $600 or something. I usually set it somewhere in the 60s and I'm in my happy place.