This is a list of the easiest to train small dog breeds. If you want a small dog that's easy to train then pick one of these breeds. The breeds in this list learn commands very quickly.
Keep in mind that just because some breeds are fast learners and easy to train compared with other breeds it doesn't mean they are more intelligent than the other breeds. Ability to learn commands off a human quickly and intelligence are two separate things. For example, a slower learning breed may simply be more stubborn or strong headed when it comes to training or get bored more quickly and therefore take longer to learn the commands. But that breed may very well be just as intelligent as any of the easy to train breeds below.