My /etc/hosts file on the machine I work on all day blocks 68k hosts 24/7. No social media sites at all except Twitter. No ads.
Meanwhile, the Leechblock browser add-on stops me from using the few things I do otherwise (bits of Reddit, HN) allow between 09:00 and 17:00 which is not perfect but it's a start. Except ... I disable it a lot :(