Dreams involving friends and exes can often reflect feelings of betrayal, jealousy, or insecurity. Your dream about your best friend dating your ex might symbolize feelings of abandonment or fear of losing close relationships. The marketplace setting could represent a search for something, perhaps emotional fulfillment or closure regarding your past relationship.

The children's sports event might signify innocence or unresolved issues from your past relationship, indicating there's still a part of you that feels tied to those memories. Your ex showing up with his ex and ignoring you could hint at feelings of being overlooked or unappreciated in your current life, especially regarding friendships and romantic connections.

Overall, this dream may be prompting you to evaluate your feelings about your friendships and past relationships. It could be a call to communicate openly with your friend about your feelings or to establish boundaries that protect your emotional well-being. Consider reflecting on what your ex and your friend represent in your life and how these relationships affect your sense of self.