I've created a few videos laying out the absolute basics of the Dredge archetype. I cover what the deck is trying to do overall, how to operate the mulligan process, how to play the card Cabal Therapy, and how to fight graveyard hate.

Video series is here: https://www.youtube.com/playlist?list=PLwGy3yc_3RDTzjIuJFVE5_GYcQsWEz58d