A lot of movies have a back story. Doctor Strange in the Multiverse of Madness comes with a syllabus.
Have you seen the 2016 film, to which this is a sequel? Good, you'll need it. (Perhaps consider a refresher. Six years is a long time.)
You don’t need to watch – or re-watch – all the Avengers movies, of which only the last two feature the titular superhero/sorcerer/doctor (Benedict Cumberbatch). But it might be helpful to re-familiarise yourself with the events of 2018’s Infinity War, which sets up a critical dynamic involving the new film’s other main character, Wanda Maximoff, aka Scarlet Witch (Elizabeth Olsen).
Finally, it is really, really helpful, maybe even vital, to have seen the streaming TV series WandaVision, set in the suburban town of Westview, without…