What dog is best for me?

im a 14 year old boy with a medium to large yard. i alredy have a dog and is unaggressive. and i would like a nother dog that would follow me around everywere is a medium to extra large and does not require extreme exersise and is good with other dogs. i am willing to groom this dog every day and give it a daily walk. what would be the best purebred breed for me in the price range of anywhere from 0-600