This was a question I was just recently asked.
First off we should keep in mind that Jesus (Yeshua) was a Jew. Jewish culture at the time of Jesus accepted both monogamy and polygamy. In fact polygamy is a mainstay of Jewish history. Parts of the story of Jesus such as the ten virgins and his being questioned by the Sadduccees show the reality of polygamy in the culture of his time.
Real Christian Polygamist see expanded families as manifestations of the kingdom of God. It is also a picture type of the body of Christ with many parts with one head.
Many of the principles taught by Jesus make a great guide for family development.