Reddit r/dogs and r/puppy101 both have really fantastic resources about how to find a reputable breeder or shelter, and other tips for how to find a good match for you and how to prepare to bring a dog home. Browse through both of them and you can decide whether you want to adopt or go through a quality breeder. They will help you avoid a backyard breeder or puppy mill. Definitely never buy from a store as they are always puppy mill dogs, and pretty much any breeder you see advertising on social media will probably not be a reputable breeder either.

Keep in mind if might take longer than you expect to get a dog. Reputable breeders often have waitlists. And going through the shelter route may also take a while to get vetted and find a good match for what you are looking for if you want a small dog. Good luck!