The current run of X-Factor is available here. I recommend starting with the ‘Prelude - Madrox’ issues and then reading all of Peter David’s X-Factor issues (starting at #1 but then renumbered after #50), but if you want to jump straight on in there, issue #244.1. is a great place to start.
I have collected the following older issues of X-Factor (from the 1990s) for their RicStar goodness: #34, #43, #44, #49, #56, #59-70, and X-Force Annual 1999. They can be found here. Read at your own risk, as older comics have art and writing styles that modern readers may find a bit difficult to swallow.
These two are reasonably easy to trace back to their origins, despite Shatty’s complicated origin story. They have a relatively short history (debuing in the ’80s) and only appearing in two books. For a long time their friendship was read as a coded romance, many fans believing they were romantically linked, and this was confirmed by Peter David in X-Factor #45. I’ve collected some screen caps and download links for anyone interested in reading up on these two :) As always, if you can afford to, please show your support for the creators by buying their work.
Warning: this post is made up of caps from early 90s comics, and contains gratuitous ponytails and pouches. If Liefeld-esque art bothers you, join the fucking club, but read it anyway because how adorable are these babies.