I do not own a single Mac eyeshadow! I don't know if its worth the extra money just cuz I feel like the eyeshadow I use does the job quite well! Although I hear such good things about Mac eyeshadow that I am thinking about giving them a try!
Some of my fave are:
Stars N Rockets
For beginners if you have never seen MAC eyeshdows in person/or if you have. I recommend you go to the MAC counter yourself and look at all the colors and swatch and see which ones that you like best for yourself.
I know a lot of the popular colors like All That Glitters etc. I was not found of when I saw it in person. Plus online the coloring of the shadows is off.
hope this helped :D