Key Collector added a "Bry's Comics Presents" post today which consisted of a list of X-Men pick-ups for under $25. I don't want to sound too critical, but I'm fairly certain he just peruses through books already on Key Collector and reposts them with a sentence he adds trying to make them sound relevant.
That being said, I'm going to give this whole X-Men pick up for under $25 thing a shot and mention a character that has multiple things going for her but doesn't have her first appearance listed on Key Collector. She wasn't a member of the X-Men but neither was Apocalypse who is on Bry's list so here goes:
The first appearance of Vertigo in Marvel Fanfare #1.
1) She's had 46 comic book appearances.
2) She's from the Savage Land which was recently hinted at/shown in the Dr. Strange trailer.
3) She was a member of the Marauders which is a storyline I could definitely see a X-Men movie touching on at some point.
4) She's got Magneto's DNA in her (not from sex).
5) She was in the X-Men Animated Series.
Now are any of these good reasons to pick up her 1st appearance? Probably not.