Affiliate since: 12/31/1969, Power Rank: 99999999

This is an interesting question, although I cannot answer it. Why? You haven't told us about your league! How can we know how to promote it until we know what your league provides? Are you offering prizes? Are you creating a league forum to discuss the game among competitors? Providing stats? All of these things can provide the motivation that will make your invitation--and your league--worth someone's time.