Ok, so, first of all I LOVE GCCs! They are my FAVORITE kind of pet, even though I am a huge dog lover and horse fanatic, I would recommend them as a first pet, last pet, and every pet in between!
Ok, First, pick a color. Look at the mutations and find one that you just CANNOT live without. For me that is all of them
There is no personality difference between colors, though I have noticed that the turquoises I have seen tend to be a little bigger, but that could just be by chance.
Ok, yes, good job, research the PANTS off of this before you dive in. Decide if you want to rescue/adopt, buy from a breeder, pet store, whatever. Many people will tell you to go hand fed, and that is fine, but it is not the be-all-end-all of pet birds, taming one yourself is very special if you have the time and patience for it. My snuggliest, bravest, cutest, funniest GCC is a turquoise named Buddy who was never handle for the first 2 years of his life. You will get bitten, yes, and it will break your heart but earning trust is worth it. So research and choose, but keep in mind no matter where you get your bird they might not feel safe, and you might have to "tame" them even if they have been hand fed.
Ok, find a cage. Pick the biggest one you can afford and then save up until you can double it. We all love our fids and want them with us as much as possible, but there are going to be times when your bird is confined to his cage, like when you are on vacation, at work, or if you have other pets like dogs and cats that could potentially KILL you baby, but who also need attention. For me, I try to make sure my birds have room to actually FLY across the cage, like, at least 3-5 wing-beats. People who have Macaws probably cannot realistically do that and still live in the same house as their birds, but with a GCC it is not too hard. Pick a cage with bars close enough together that your bird cannot stick his head out between them. I like to get long cages rather than tall, so I can put perches on either end and leave flying space in the middle, but I also like my birds to be flighted rather than clipped (big can of worms I won't get into here, I do believe in clipping in some situations, in fact I clipped one today. I just dont think it is best most of the time).
Speaking of clipping, decide if you will or not. Read material on BOTH SIDES of the argument, think about your lifestyle and living situation, etc, and make a choice whether you will clip or not. Ask advice from other people, but ultimately you need to choose.
READ READ READ but make sure you are reading GOOD stuff, not random garbage from people who don't really know. This forum is GREAT for advice, but do other research as well. I highly suggest reading everything you can get your hands on by Dr. Steve Hartman of Hartman Aviary. This is the only man in the world running a breeding program aimed at ACTUALLY DOMESTICATING parrots, he also is the inventor of the Aviator Harness which I swear by. I would post the link but his site has things for sale so we are not allowed to post it here. The Parrot University is the other thing he runs, google them and read away! This is the one in Ohio, the one in SC is not related as far as I know. Also read everything you can by Barbara Heidenreich, of Good Bird Inc. She is a world-renowned animal behaviorist and trainer and offers a lot of REALLY good advice. Sign up for her free stuff! Like how to train your bird to let you clip his nails, or give him medicine! A lot of people claim to be experts, make sure you read things by people who actually ARE experts!
My GCCs are mostly quiet as long as they get fed on time. They yell in the morning and evening as the sun rises and sets, and Flick flock calls if she is left in a room alone. Typically the bird's noise level will mirror that if the house. If my husband and I are trying to have a conversation from two different rooms, Flick ALWAYS interrupts. When we yell, she yells! My IRNs are always loud when there are kids over, but then again the kids are always loud. They are generally considered a good bird to have in an apartment, but you can never make that promise that the bird you are getting will fit that stereo-type.
As for diet, there are some main schools of thought. Most common right now is the idea that a bird should be on a pelleted diet as the main food. Others feed only seeds, and some feed only fresh food. Most people believe seeds alone to be far too fatty, but I have also heard that a high quality seed diet is much more natural than pellets. We know that for humans the less processed the food, the better. Personally I prefer to feed fresh veggies (fruits only as treats of when transitioning a bird to fresh food) as the main food and supplement with pellets (especially during breeding season or stressful periods) and feed seeds as treats along with fruit.
ok as far as deciding if the GCC is the right choice:
Pros: Small, inexpensive, quiet, smart, curious, not that big of a beak, not "too messy" as far as parrots go, they come in SO MANY colors! They have a reputation for being really snuggly, but they can be acrobats as well. None of mine are "one person" birds, or even "one bird" birds.
Cons: They have a reputation for being "nippy" however none of mine are. We had a period of time when Flick was, but as with any behavior problem, there was a cause. Always look for a cause when there is the problem, rather than assuming it is the animal's fault. An old boss of mine used to say about horses that if something was going wrong you ask yourself 3 questions "Is it me?" Am I doing something to cause this? "is it the equipment?" I substitute health here, get a problem bird check out by the vet ASAP, and consider whether the bird i getting enough sleep, play time, and the right food. And then he would say "Is it the horse (bird)" and he would always emphasize that it almost never was the animal just being a jerk for no reason. Ok, I admit, the only real "con" to a GCC is if your heart is set on a different bird. Really, if what you want is to "work your way up" to another bird, dont get a GCC because they can live 30+ years and they deserve to be your bestie that whole time, not be replaced by a bigger/flashier bird, or one that is more likely to talk. GCCs can learn, but many never do, btw. Generally as volume decreases so does talking potential.
Do you have any specific questions?
I love all my birds, but the GCCs steal my heart every day. They all have different personalities but "cheeky" is the word that comes to mind to describe them best. I have one who wants to lay on her back in your hand and take a nap all day, another doesnt care what happens as long as he gets FOOD! RIGHT NOW! GIVE ME THE FOOD!! Another is a velcro bird - if she could spend all day on your shoulder getting in the way of everything, she would. Also, your drink is her drink, no matter what it is. I have 2 that came together and I am the 5th place they have lived: breeder, pet store, first home, second home, then me. The second home was with a filthy mean woman who I believe to be a hoarder, and I believe she sold me the birds because she was out of food money. These two are STILL sweet as can be! One of them does not like my husband very much for some reason, but even then is not really nippy, just kind of snappy if Josh tries to pet him. They are so smart and eager in life! 
