Mixed breeds are the best :) If you want a very docile medium dog breed, try whippets :) Poodles are great as well. Remember, dogs are a product of your environment and training. There is no bad dog, just ignorantly trained humans who ignorantly train their dogs.
All breeds are good.keep in mind though,each breed is bred for a particular purpose.Some are good with kids,while others are not.Most are very active and were originally bred for hunting purposes.Also keep in mind how much room and time you have fir the dog.Are you active?Do your activities include those that a dog can join you in?I have had many animals,please conceder adopting from a shelter first.There are so many sweet,faithful friends in need of a second chance at life.My personal experience had proved that adopted animals make better friends.They know you helped them and are truly grateful in return.
According to American Kennel Club, there is a list of about 10 most popular dogs you can choose from; there is the boxer breed, Shih Tu, miniature Schnauzer, Dachshund, Beagle and German shepherd. There is also the Labrador retriever breed, Yorkshire terrier and the golden retriever. You can go to, http://www.justdogbreeds.com/,and see the best breed that fits with the requirements and conditions you want.
Personally, I prefer mixed breeds but all different breeds are bred for different reasons and also, there are many different health risks that dogs can have and it also depends on the age of the family you have around. For example, a Chihuahua may be small, and cute, but they also have a ton of health risks and are extremely fragile and can be extremely loud and too "big and bad" for their own good at times. It really depends on if you want a "lap" dog, a dog to run and exercise with, and your own connection with the dog (you'd be sharing your home with him/her, therefore, the dog needs to be one you're comfortable with and you can take care of). I know you've probably heard this many times already but I'm saying this because my parents picked out my first puppy which was a pekingnese without even realizing how much care a dog her size would take and that she would probably have been for an older family whereas our second dog, I found abandoned when I was around 8 and it was the perfect dog for us, energetic, small, barked but not too bad, obedient, and other than grooming we never had any problems with her...she was a schnauzer by the way.In other words, go to some local trusted breeders, local humane society, or look around to see who else has any puppies. Hope you found some breeds of dogs to narrow your options down to even if this didn't help^_^
Oh and P.S.: be very careful about going to a pet store and buying a puppy unless you want to risk extra vet bills...if you can afford it, GREAT, you might mean a better life for a puppy who may very well of been bought from a puppy mill and the dog might be fine but many pet stores do buy from somewhat untrustworthy places such as puppy mills.
I have a chocolate lab cross with golden retriever and he is only 14 months and he is absolutely adorable yes he will be a big dog but get him or her when the are young that way you can train them yourself