It can be very tempting to get a snake from a chain store, and I agree that it's easy to fall in love with the pet store snakes. It's incredibly important to get a pet you like. After all, you're going to take care of it for the years to come.
However, there's another side to that. You need to make sure that the entire experience is pleasant for you. What if the snake won't eat for you? Petsmart most likely won't do anything for you. What if it dies? Would you ever trust yourself to own another ball python? A ball python can bring so much entertainment and enjoyment to people, but it has to be the right python and the right owner.
Here's an idea. If you want to make sure you get a friendly snake as your first, and decide not to go with a chain store, how about you talk to a breeder on the phone and ask them to find a snake in your price range that is fairly docile? That might be the right way to go. If you describe the personality you want, I'm sure many breeders, though perhaps not all, would be willing to work with you.