The truth is in the comments. The heavily promoted products are easy to find, but the real gems are often in the weeds. The gems are mentioned by people who don't make money off them, usually. They just want to help people out.
That reminds me the famous lines from Thomas Gray
Full many a gem of purest ray serene
The dark unfathom'd caves of ocean bear:
Full many a flower is born to blush unseen,
And waste its sweetness on the desert air.