I'm catching up on this on Marvel Unlimited. I had read HoX/PoX when they came out but stopped the main series after Professor X was killed outside of the main books. I didn't feel like buying all the side books if hat was was was required and figured I'd wait until a good chunk was on MU, and here I am!
So my question is, after Dawn of X do I need to keep reading the other X books besides ones I just happen to like, or am I good to just read the main stuff by Hickman?
Skip Fallen Angels for sure. The Wolverine and Cable solo books are both decent books, but superfluous.
New Mutants and X-Force are both great, but are surprisingly less essential to the main storyline than you'd expect.
X-Men, Marauders and Excalibur are the main essential titles as you head down the road to X of Swords.
X-Factor and Hellions start later, and both are a lot of fun, but are side gigs for sure.
Note that once you get to XoS, however, you'll need to read all the parts as it makes its rounds through all the books.
Honestly though, Fallen Angels was the only stinker for me in the whole line... I think everything else has been worth it.