A few years ago, while working on the now defunct VeXed-Men website, I did a series of The X-Men in ten seasons, where I did some exhaustive reading, some skimming, some Wikipedia-ing, and some trips to the used book store that carries comics, and put together an exhaustive timeline of how to read the X-Men using pretty much all of the trade paperbacks that were then available.
Don't do that to yourself.
In the last few months, I've read nearly 150 X-Men and X-Men adjacent books including spin-off titles such as Cable, X-Factor, X-Force, X-Man, Generation X, Rogue, Wolverine, Wolverine & Gambit...if it has been collected into trade in the last fifteen years or so, I've read it and reviewed it on Goodreads, and it made me question why I ever even liked the X-Men.
It has taken a long time to figure out a season four. I read so many books in the last couple of months that raged from terrible to absolute masochism. Part of the problem is the art direction for this time period in Marvel is atrocious. Everything is dark and muddy. In some books, particularly the X-Force run, which I've excluded completely, you often can't make out which character is which because it's SO DARK. Eventually, though I found some great stories, particularly the Peter David X-Factor run. Most of this season will center around Hope, the first baby born after the Decimation, and how her existence changes everything for the mutant future.