Pick up the X-Men Essentials. They are the consecutive collected issues starting from issues 94 which was when the new team (Wolverine, Storm, Colossus, Nightcrawler, etc) join the book and the great Chris Claremont sarts his epic run.
I have Vol's 1-7 which i think ends around issue 180 something or other. These books include such great stories as the Pheonix/Dark Pheonix saga, Mutant Massacre and The Brood saga. Epic X-Men if there ever was.
They are unfortunately in black and white but for about $25 you get a book with usually 20+ issues in it. Great stories at great value.
I also recomend the Spider Man essentials but honestly the X-Men ones are better.