Seems like you still have a lot of reading to do
Sincerelly, the Stan Lee/ Jack Kirby years of X-Men were some of my least favourite, the writers that came after did a better job with the characters and ideas.
Either Way now that the characters are gone of the way lets go to the comics that inspired the movies.
The first film wasn't actually based on any single comic book, it's kind of a mesh of ideas to start the franchise with but it certainly had some inspiration from the 90s X-Men cartoon:
Bryan Singer himself saw the show before making the movie and this was one of the reasons why he began to like the X-Men and decided to make the movie.