there are so many shades in every color you could possibly almost imagine, that it's hard to tell you what shades are must-haves. Here's some I have that I love, but it also depends upon what shades you gravitate towards, but the good thing is that you can buy some shades you wouldn't normally try as pops of color or to try something different.
Some of my faves:
428-pearl violet, 482-shimmer navy,433-green bronze pearl, 53-brown gray w/sparkle, 446-plummy pearl, 379-matte lilac, 433-pearl khaki,338-deep teal matte,12-orangey rust pearl, 498-deep pearl gray, 420,-MAC moth brown dupe, 460-lite brown taupe, 57-forest green, 390-matte beige
Even if you have ordered shades that you dont' think will liek, try them anyway, or you can always swap them! They are very popular on the swap sites.
You should also try the lip pans for $4 a pop - they are all quite opaque, and I mix the colors sometimes to make my own shade. They wear so well that I sometimes dont' even use lipliner, and I have small wrinkles around my lips. Remember, these are the PANS, not the lipstick bullets nor glosses.
Good luck!