I think the dog breed is very important -- assuming it is a pure breed. That's the reason for breeds. With enough attention, the breed traits can be overwritten. There is also a natural spread in the behavior range and working/pet/show lineages to consider. For the average pet owner though, it is easier and safer to stick with pure breeds that have traits favorable to being a pet. Most people should play the odds and stick with the popular pure breeds.
Amateur dogs. These are breeds I would recomend for pets:
Golden or labrador retrievers have a consistent and mild temperament. They are adaptable. As long as you heavily exercise them every day or 3 and are friendly with them, you don't have to worry much about misbehaving. They almost train themselves. Serious problems like biting, chewing, excessive barking, running away, or seperation anxiety just don't happen if they get that occasional heavy workout and are treated well. They are readily available and are almost always healthy. They shed but don't need brushing and don't pick up mud or brambles. Puppies sell for $50-$200. They are good for owners with a busy but outdoor active lifestyle.
Spaniels have similar temperament. They are much less active and smaller. They require attention to coat, ears, and eyes. They are expensive to purchase and maintain. Many suffer from chronic health issues. Cockers are good for older people who can get out and walk but not necessarily work the dog hard.
The setters are real sweet. They are less active than the retrievers. They need daily moderate exercise rather than infrequent intense workouts. They need to be around people else they chew and dig. They tend to be healthy. They are good for households with busy stay-at-home moms.
Expert dogs. These are breeds I would not recomend as pets unless you have time & patience to train it or have acreage for it to run. Many of these dogs find their way to the pound because they are not trained properly as puppies.
Anything with "shepherd" or "collie" in its name can be overactive and agressive. These dogs need to be socialized when young else they become protective, snappy, yappy, mean. Also, ranchers still use these dogs in the west and midwest so you are more likely to find a dog from a working lineage rather than a pet or show lineage.
Anything with "hound" can be difficult to control and is going to bark and disappear over the hill on you.
Anything with "pointer" needs heavy and daily exercise. They are expensive to purchase and hard to find actually. The books describe these dogs as similar to retrievers and setters, but I think in the west they are bred only for hunting so are high strung.
Anything with "terrier" needs to have a moderate level of attention or activity throughout the day else they get bored and misbehave. Same for poodles. Poodles are clean. They don't drop hair all over the house. The hair must be clipped. Poodles live a very long time.
The small breeds frequently have disagreeable personalities and seperation anxiety. Everybody in the house hates it except its champion. Usually mom or sis. Since they are so small, they are minor annoyances and they are easy to pawn off on other people when you go on vacation.
The very large breeds have health problems and dominate the house(cleaning). They are docile. They do well with little attention. Any trace of agression has been bread out of them.
Guard dogs: Rottweilers. Dobermans. Akitas. Yeah, they can be great. You have to train them so well or keep them in protected environments else you'll be staring at a lawsuit or a visit by a control officer -- whether deserved or not.
Mixed breed mutts: Who knows? They certainly tug at the heart strings when you see them in the pound or superskinny wandering down a side street because you know their likely fate is the gas chamber or needle. And, you probably grew up with one as a kid -- especially if you are old enough to remember the 70's.