I think you need to make a list of your requirements, apart from just size, i.e. long or short coat (are you prepared to groom or pay to have clipped), are you prepared to train (do you want a small working breed or one that is just a lap dog), are you prepared to give lots of exercise ( are you active or a couch potato), have you a fenced garden (some breeds are escape artists and/or will not come back if let off the lead).
Also you must decide whether looks are important (by this I mean some people don't like the look of some dogs, and some men may not want to be seen with say a poodle (although there is nothing wrong with poodles - a very intelligent breed).
Cost is another thing, the rarer breeds are more expensive, whilst some breeds are easily available and there is a lot of supply to satisfy the demand, therefore the cost is lower.
Whatever you decide, please go to a reputable breeder, the best way is to contact the breed club and ask for a list of club members who may have a litter due. Make sure all health checks are done and that the puppy is registered (you get what you pay for - a 'cheap' puppy may not be what you are expecting as others on this group have found out to their cost).
Please avoid puppy farmers who only breed to make money without any interest in the breed or its health requirements.
Remember, your puppy could be with you for anything up to 15 - 20 years (my dog's dad died last week just short of his nineteenth birthday). Make sure they are happy years for you both, rather than a nightmare because you didn't get the right breed for you.