You'll need a coop with 2 or 3 square feet of floor space per bird, plus area outside the coop (a run or free range) of adequate size. Ensure that their enclosure(s) are predator proof, mouse proof, snake proof, owl proof, you get the idea proof! Know that if they free range, eventually one or several will not make it home; it's the tradeoff, but you need to prepare for it.
Determine where and how much a veterinarian is in your area, preferably an avian veterinarian, but at the very least one that specializes in small animals (not just cats and dogs). Not saying that you'll ever NEED the veterinarian, but if you should ever need them, you have a reasonable expectation on costs to help you determine if you'll treat at home or seek a professional. Even if a vet does not see chickens, ask them if they would write a prescription for medicine for them if needed, if you provided the doctor with the name and dosage information. You can often get that information here at BYC. You've nothing to lose by asking, but might find an ally for the health of your flock.
Adult chickens consume about 4 ounces of balanced feed daily, and what baby chicks don't eat is wasted as they poop on the extras, so might as well call their needs at 4 ounces daily too. Buy enough medicated chick starter to get you through six weeks (4 birds per pound of feed by 42 days); that's 10 1/2 pound (4.75kg) of feed per bird to get them from hatched to six weeks old. Buying a METAL trash can with lid to store the feed in will greatly reduce the likelihood that vermin, rats, mice and others looking for a free buffet, from moving in (and spoiling your feed). While discussing feed, after 6 weeks of age, you may consider switching them to non-medicated chick starter or start switching them into an all flock feed. I prefer all flock with crushed egg shell (or oyster shell if your feed store carries it) on the side for my girls. Medicated feed contains amprolium which significantly reduces their uptake of B-vitamins (but starves cocci to death, while the bird develops a resistance to the parasite); It is not meant to be fed for their lifetime as that would be detrimental to the health of your flock.
Speaking of cocci. While you're at the feed store, purchase some amprolium (that's the generic name of the medicine) in case they suffer from an outbreak despite consuming medicated feed. Cocci can kill a chick rapidly, so having the medication on hand (it's cheap) is worth it. Also, pick up a can of blu-kote in any color except for red for wound care and camouflage.
You'll need to read/watch everything you can about hens and reproductive disorders so that should one of your girls have a problem, you'll recognize it and know what to do. Do the same for bumblefoot and how to deal with it. And parasites. Just saying, arm yourself with knowledge on what bad things CAN happen so that IF they do happen, you're not the one running around like a chicken with their head lopped off.
Decide here and now how you'll deal with cockerels (boy chickens under 1 year old), is it legal to keep them where you are? If so, do you WANT to keep ONE? If not, will you be re-homing or butchering him/them for the dinner table? If you are going to eat your birds (I do), it helps to name them after food so that it's a tiny reminder daily on their ultimate purpose; to put food on your table.
@Tycine1 has great startup advice! A lot of that stuff we learned as we went, it is so nice to have it all in one place!
As far as breeds, it depends on what you are looking for. Are you just looking for eggs? Meat? Are they pets? We went the pets and eggs route, we love our Easter Eggers, they have been relatively friendly and having different color eggs is fun. They are good for hot weather, and cold weather so they tend to be hardy. We started with Buff Orpingtons too, but they were tough to keep cool here and they died before they were 8 months old. Be aware of your temps. We can sustain large body birds here now, but it's embarrassing how much money we put into making that happen so I wouldn't recommend it to most people. I would do plenty of reading on breeds, look closely at aggression ratings, if you want multicolored eggs, look for that. We have birds that lay green, blue, white, dark brown, speckled brown and light brown eggs. As a beginner maybe look for birds that are not going to spend a lot of time being broody, it can be intimidating to try to break a broody hen as a beginner, it was scary for me, I had to do it with oven mitts . As it is now our girls range from friendly to needy lap chickens. Our breeds are listed below my comment, all but our Golden laced wyandotte and our white crested black polish are super sweet, but all chickens can vary and have different personalities within breed. The nicest are our Super Blue Layer, and our Mottled Houdan. Reading about the breeds and asking people about them is so fun! Let us know how you are leaning!