We had a border collie mix that was the most lovable dog I have ever met. She was also dumber than a box of rocks(probably her mixed part, as every other border collie we've met is smart), which made her even more lovable. Got her from the pound as a puppy. Great with kids, except she'd try and herd us if we ran in the yard and we'd have to call mom to get her if we wanted to play.
We had a pure bred Cairn terrier (like Toto). He was super smart, but thought he was way bigger than he was. Absolutely fearless of other dogs, despite his stature. Typical terrier. Easy to train, small size, very interested in human life. He was too big to breed (very specific sizes in that breed specs), so the breeder gave him to us for free.
I had a collie mix that we found as a puppy. Great mellow dog. Learned a lot of tricks. Got along well with humans. My best buddy for 14 years.
We had a collie mix, again a dog pound dog. The previous owners gave him up because he was supposedly untrainable. Without a doubt, the smartest dog I've ever met. Sit, stay, shake hands, shake other paw, lie down, roll over, roll over the other way, play dead, dead dogs close their eyes, COUNT! 1 finger 1 bark, 2 fingers 2 barks, 3 fingers 3 barks, 4 fingers continuous bark until told to stop. Climb a ladder. Jump through a hoop. Go to the end of the driveway and get the newspaper from the carrier. Take the paper to anybody that you'd name. Point your finger at someone, snap your fingers and yell WARN EM! and he'd bare his teeth at that person and growl. Saved my mom from a car jacking attempt. Bit the heck out of the guy.
All of them were great dogs. Only one was a pure bred (the Cairn). All got along with people, other dogs, and our cats.
I'd say unless you have a very specific reason to have a pure bred dog, there are so many mutts/mixed breed dogs in shelters in need of a good home, I'd go that route. Most shelter dogs are already accustomed to other dogs, multiple people, and group settings. It's a good start
Good luck in your search.