For my browser, AdBlocker Ultimate. Does a good job.
I also use Firefox containers. The purpose of containers is to hide web activity from snooping websites. For example, if I use Facebook, I use a special container, and as such FB never knows what websites/searches I do otherwise.
I also use Portmaster, which allows me to see every single connection/request a website/application makes (and shut them off or make rules for them), also contains an adblocker.