I suggest spending some time on:
https://www.reddit.com/r/Mattress/
now that said, I had an extreme budget for a guest room mattress that I've slept on 30+ times (and am also a side sleeper), and have been very happy with a (full size)"Brooklyn Bedding Standard 10" full firm hybrid" which was, and still is, under $200 on a website I am not allowed to link to, but will probably be the first result if you search for exactly what I wrote.
Brooklyn Bedding. I’ve had mine for a year with no regrets. I bought the firm with a cooling top. I was leaning towards the medium but based on other reviews I chose the firm. Fortunately it is not a hard, it does have good support and bounce. I sleep on my side and back and any hip or back pain I had disappeared. Im 5’10, 170. I rotate it every month or two.
I got a twin x-long mattress from Brooklynn Bedding. Then I got a second one and now they equal a king sized. I got a set of 2 wood frames from IKEA. And now I have a great king sized bed. Easy to move too because it’s basically modular.
If you run hot, I’d check out Brooklyn Bedding or Plank before grabbing straight memory foam. BB hybrids move air way better so you’re not waking up sweaty. Plank helps too since you stay on top of the mattress instead of melting into it. Makes a big difference at like 3 AM when everything feels warm. I’d test a medium-firm hybrid at home and see if it keeps you dry.
For that budget Brooklyn Bedding or RV Mattress are better value than Nectar. Factory direct so you're not paying markup. Both have home trials. About the FB Marketplace ones, prob overstock but you're gambling w/ no warranty. Buying direct is safer.
When my wife and I were mattress shopping, we relied a lot on the analysis from Sleepopolis https://sleepopolis.com/
One person's perfect mattress is another's chronic back pain, so it's not a wise item to crowdsouce. This site has videos that show different types of sleepers, where the pressure points are, and how it's likely going to affect you long term. I like data driven analysis and this site is full of it.
We ended up going with a Brooklyn Bedding Hybrid (spent like $1,200 on sale) because it had the features we wanted: cooling, good edge support, you won't disturb the person next to you if you get up, firm enough for support and bounce but still soft up top. I'm very happy with it, and would recommend it if those are what's important to you. But you're different, different body with different needs. At the end of the day, we're spending close to a third of our lives in bed. You can only cheap out on that so much.
BSDC
