When you are starting out in collecting, the number of titles and graphic novels can be somewhat intimidating.  I have foudn that the best way to start is to pick a character that interests you (maybe one from one of the big movies) and check out a few graphic novels.  I have listed a few heroes and a key tpb or two to check out)

X-Men:  check out the Astonishing X-Men series (Joss Whedon) or Days of Future Past (Chris Charmont)
Superman:  Superman: Under a Red Son
Batman:  The Dark Knight Returns (Frank Miller)
Green Lantern: check out the Green Arrow/ Green Lantern run (not sure what the TPB is called, but your comic book shop can help you)
Daredevil:  Frank Miller's run in the 1980's with Elecktra (not sure what the TPB is called, but your comic book shop can help you)
Captain America:  Ed Brubaker's run
Spider-man:  check out the Ultimate Spider-man series
Hulk:  check out World War Hulk
Horror:  Walking Dead series by Robert Kirkman
misc:  Watchmen by Alan Moore
Buffy the Vampire Slayer Season 8


Also, the Essential collections are another great bargain.  the reprints are in black and white, but they collect around 30-40 issues for under $20.

Another thing to do is to check out sequentialswap.com and trade with other members.  This will allow you to check out a lot of titles and not break the wallet.