In Act II, scene i of Christopher Marlowe's play "Doctor Faustus," Mephastophilis states that "marriage is but a ceremonial toy." This has been defined by critics to mean that he believes that marriage is a trifle (trifle- something which holds little value). Therefore, Mephastophilis is simply saying that marriage is not necessarily worth anything.
One can look at this in two very different ways. First, a marriage is not what insures the success in a relationship. People do not necessarily need to be married in order to have a successful relationship. In essence, a marriage is simply a ceremony which publicly shows one's commitment to another. In Mephastophilis' mind, some may not need the ceremony to define their commitment.
Another way this can be defined is that marriage is simply valueless. By marrying, one limits their possibilities. Given the conversation surrounding the quote is speaking about courtesans (female prostitutes to those in high courts), Mephastophilis is reminding Faustus that he is limiting his opportunities by considering marriage.