Welcome to BYC! As All Henned Up says, clean the coop thoroughly, or get rid of it. You don't want to introduce chickens to a coop that may be infested with lice or mites, or any diseases the other chickens that were in that coop may have had.
For starter breeds I highly recommend Buff Orpingtons. They are very sweet towards people, great layers, and very pretty. I have 5 and I absolutely love mine. Another breed is Rhode Island Red's. Not as sweet as Buff Orps, but great layers. You can also look into Easter Eggers.
How many chickens you get is up to you. It depends on how many eggs you want, how many can fit in your coop, and how many you can afford.
Good luck!