You need to weight the pros and cons between buying a puppy or adopting an older dog. Giving an older dog a home is great act but you don't know about their past. I know that my mom tried to adopt an older dog while I was about six or seven. At first, the dog was really nice and friendly until it was adopted. Once it was home, it would chase me around the house and corner me while growling and biting. It slowly became to aggressive to have in the house and around me that my mom was forced to give him back. The shelter only then told her that we were the third home to return him because of aggressive behavior. So, even if you bond with a dog at a shelter, it might become another dog when you get it home. If you aren't prepared to deal with any of the psychological issues that you dog may be suffering.
The only exception might be adopting puppies from a shelter or a home that can't keep a litter. This might be ideal because you can rescue a puppy and give it a good home for perhaps a cheaper price than buying a dog. There are usually posts on Craigslist for puppies in your region.
Buying a dog from a pet store has benefits because most dogs have papers and a history. While there are some ethical issues with puppy mills, you can do some casual research to find out if your store buys from ethical breeders or not. The price is another point that can hurt if you get a purebred dog. But you get a puppy or dog that doesn't have a history of bad habits.
Personally, I would go shopping in both pet stores and shelters. Meet as many dogs and puppies as you can and see if you bond with any of them. If those fail, try looking into Craigslist to see if there is a dog for you there. You might be able to find a dog that is already trained and has its shots or new puppies. When you meet the right dog, you'll know. But I would make a list of things you are willing to deal with and things you are not. From that list, picking between adopting and buying should become more clear.
