The safest bet is reading Grant Morrison's New X-Men and then Joss Whedon's Astonishing X-Men run that continues it.
I love New X-Men. Morrison pretty much took 30+ years of comic books history, gave it a fresh coat of paint and doing so defined the next 25 years of mutant shenanigans. Whedon picks up where Morrison left off sans the punk spirit and a bigger focus on action; pretty much what you probably think of when you imagine a standard superhero comic.
Chris Claremont picks up with Giant Sized X-Men (Followed by X-Men #94), but I wouldn't reccomend it as first contact unless you're used to comics of that era, it can get very wordy. The material gets exponentially better after the first couple of issues, though, so whenever you get around to it simply start on GSX-M and enjoy the next 140 books, give or take