Well I haven't watched Doctor Strange yet, nor any of the movies in the Marvel series, and I was wondering if I can watch Dr. Strange without getting lost about the storyline in case I need to watch some other movie to have an idea of what is going on.
No, it is not related.
Well.... it is set in the same Universe as the other Marvel movies.
But, apart from a couple of brief mentions, nothing that happens in the film relates to the any of the others.
The film is a self-contained story, and you will be able to watch it without knowing anything about the other Marvel films or comics.
That said, it is part of the story leading up to Avengers: Infinity War, so if you're planning to see Infinity War, include this one.