Without knowing anything about you at all, it's very hard to recommend any products to you.
Why do you want MAC products? Just because people say they're good? They may not work for you. A lot of MAC foundations/powders break my clients out. PLEASE, if you have never used MAC before, go to a store or makeup counter and try things out/talk to a specialist. Do not ever buy a product just because someone says to, buy one because it works for YOU. =)
Here are a list of things that are very general that I think everyone should have:
Eyeshadows:
1. Brulee
2. Sable
3. Copperplate
4. Carbon (everyone should own a matte black)
5. Woodwinked
6. All That Glitters
7. Phloof
8. Satin Taupe
9. Scene
10. Shroom
11. Naked Lunch
Pigments:
1. Melon
2. Vanilla
3. Mulch
4. Club
5. Malt
6. Vex
7. Ricepaper
8. Honeylunch
9. Espresso
Brushes:
These are very taste specific, but I couldn't live without these:
Face:
129
187 (foundation)
188 (blush)
Eyes:
210
219
239
217
222
224
208
Foundation/Concealer:
You really have to figure out what's best for you. My favorite MAC foundation is the Studio Sculpt, but I can't stand the texture of the S.S. concealer. The Studiofix is great as well. I'm not sure what to recommend for you as again, I don't know anything about your skintype.
If you're looking for a powder foundation, their mineralized skin finishes (MSF's) are great. Get matched to your color at the store/counter. They're lighter coverage, but I think most people wear their makeup too heavy these days anyway =)
The huge gripe I have about all of MAC's foundations, though, is that they tend not to last very long, even when set with fix+ and/or powder. The PH balance must not match with a lot of people's skin chemistry.
Blush:
Their cream blushes are GREAT! I love putting cream blush under powder blush, it gives a great effect. Posey and Sweet William are my favorites. My favorite powder blush from MAC is Pinch o Peach.
Liner:
MAC's fluidlines are amazing. The tecknakohl liners are also a MUST have. However, since you are unfamiliar with MAC, I suggest you try them at the counter. I think Urban Decay makes better Kohl liners than MAC and I think they're a couple dollars cheaper. Yeyo and Zero by Urban Decay are my favorite liners.
Lipstick:
Lipstick is one of those things where I'd have to see you to recommend a color. I think the most universally flattering ones, though, are Myth and High Tea. They're very good nude lip colors. Fleshpot is very similar to Myth but a little more of a pinky undertone. Kinda Sexy is very pretty on most skintones as well.
Lipglosses:
I honestly think MAC lipgloss is overpriced for the amount of product you get.
Some random products that I love:
Fix+ (I use this EVERY SINGLE TIME I do my own makeup! I use it as a base and a finishing spritz)
Lustre Drops
Mac Wipes
Paintpots (there are a lot that I love, but I mostly use Painterly and Rubenesque)
DO NOT buy their mascaras! They're horrible.
I'm sorry for such a vague answer, but again, I need to know more about you to recommend specific products =)
Good luck!