Hi! Good to hear you're becoming a MACaholic...I suppose it's the only GOOD type of -aholic out there.
The necessities (for me anyway) are good brushes, good eye base (MAC Paints, Cream Colour Base), good foundation (I like the various Studio Fix), and good mascara.
For brushes, they can be a bit costly, but believe it or not, they technically save you money in the end. Sponge applicators suck up a bunch of your product that you will never see again, so you can buy less make-up after a while. And if you take good enough care of your brushes, they can last quite a while. Figuring out which brushes to start with really depends on what you're planning on emphasizing most about your face. For the eyes (which require the most brushes), you'll need a shader brush (239 is my personal fave), and blending brush (I use the 217), an angled brush for filling eyebrows and applying liquid eyeliner (only if you plan on doing this, some people prefer not to...the 208 is good for both functions). Also, pencil brushes are quite handy as well for doing crease eyeshadow (the 219), though you can get by without it. For the face, the 187 brush is wonderfully multi-functional, you can use it for both powder and liquid foundations, as well as blush. The 190 brush is best mainly for liquid foundation, and angled brushes work best for blush (such as the LE Raquel Welch brush). If you really wanna get fancy you can get a buffer brush (such as the 180 or 182) to really blend your powders together beautifully. As for lips...well I can't say I'm personally a big fan of lip brushes, so I can't really help you much there. I believe MAC only sells three, one one liner and two shaders, so it shouldn't be too tricky. Now, if you were actually going to buy all of these brushes at once, it would be very, very expensive. So that's why I said you should figure out what you want to focus on. As for the very, very bare essentials...I'd say the 187, the 239, and the 217 (if you're into the liquid liner/brow filling thing, then the 208 as well) should get you off to a very nice start.
Now onto colours...
If you're into black, then you'll like the following two items: Blitz & Glitz fluidline and Black Tied eyeshadow. The fluidline is black with a very slight gold shimmer. You can't really see the shimmer when you put it on, but it softens the black so that it wouldn't look overly harsh on your pale skin. Black Tied is great for creating smoky eye looks, or darkening other colours. It's glittery black, and it blends a lot easier than Carbon does. But if you're not for the glitter, go with Blacktrack fluidline and Carbon eyeshadow. Same thing, but matte.
For colours, reddish eyeshadows such as Coppering and Star Violet would compliment your eyes beautifully. If you're looking to go really crazy (but cool, one of my favourite eyeshadows), try MAC Paint in Flammable. It looks AMAZING paired with either Beauty Marked or Black Tied eyeshadow, or gold colours. You can make this incredible red smoky eye thing, which I think would look great on you. Also, purplish colours go nicely with green eyes, try Trax (plum with bronze-ish shimmer), Purple Haze, Shale, or Beautiful Iris.
Pigments aren't dangerous or difficult, though if you're inexperienced with make-up (which I don't know whether you are or not), it's probably just easiest to use eyeshadows. You get more vibrant colours out of pigments, but eyeshadows still look beautiful.
And as for my preferred order of putting things on...I actually don't know if I do it the "right" way, but this is how I do it: I apply my moisturizer, then apply Studio Fix powder foundation (some people use liquid, then powder, but my skin is pretty good so I just use the powder, gives pretty good coverage anyway), then some sort of blotting powder below my eyes to catch any eyeshadow fallout. I apply eyeshadow base, then the eyeshadow, then liner, then fill my brows, then mascara. Then I finish my face make-up, first blending out my blot powder, then do contouring and blush, then wear lipstick if I feel like wearing any. Like I said, not sure if this is the "right" way to do it, it's just the way I like to.
Hopefully this helps you out, and that I didn't go too extreme with the colours. Let me know if you need any more help!