Priorities:
- Basic mates with rook, queen, two bishops, knight and bishop, king and pawn against king.
- Do as many tactic puzzles as you can. Tactics Trainer, google search for other resources (I'm not allowed to post links) or pick up some books full of problems.
- More complicated endgames - basic rook and pawn endgames, learning things like the Lucena position, work through classic endgame studies to see themes of creating weaknesses, triangluation, that kind of thing.
- If you've been doing this for a while and your rating starts to plateau, then it might be time to study one or two openings and work on positional play.
After a month of stubbornly ignoring all the good advice from chess.com forums about the importance of tactics and end game for beginners (and not openings!), I would now like some suggestions as to best way of doing this!