You’ll have a lower chance to accidentally download a virus and the web is less annoying.
uBlock Origin is the go-to. For Firefox, Firefox on Android and Chrome
Most of you probably already have an adblocker, but an astonishingly large amount of people don’t have one. Try it, you will never go without.
What else do you think is absolutely necessary to browse the web safely?
uBO is the best choice, I think, but it is convenient to add some complementary extensions, which also cover other aspects of the tracking that some pages use. Recommended are:
Trace - All kind of fingerprinting, header, hyperlink auditions, etc.
What campaign - Swap out Google Analytics parameters with invalid data
Site Bleacher - Remove automatically cookies, local storages, IndexedDBs, service workers, cache storages, filesystems and webSQLs, except from the whitelisted ones
All FOSS and the best I had tested
At OS level I use Quad9 DNS and DNSCrypt and ProtonVPN