uBlock Origin: Ads be gone. You need to select/add the blocklists you want.
Privacy Badger: Automatic tracker blocker with no configuration required.
Cookie AutoDelete: Saves cookies for the pages you want it to, and nukes everything else.
Firefox Multi-Account Containers: Keep your activity in separate silos. That Banking container cookie won’t be visible to that Porn container’s JavaScript, Meta’s container can only see Meta’s stuff, etc.
I use a bunch of others, but the above are my bare minimum.
Don’t believe anyone who tells you that one extension does everything.