Write him off as a bad experience and forge ahead. Don't give up on life. When I was younger than you are and still in high school, I made and had friends who later turned on me. In freshman year, people I met and made friends with were, by sophomore year, mortal enemies. A sweet girl I met and befriended later came up to me one day at lunch and told me I was being talked about because of what I was wearing and I had to go out and buy some new outfits. I wanted to be sick right then and there. I almost cried. My parents were struggling to keep the utilities on and food on the table for four kids, themselves and a mother-in-law. I wasn't old enough to go out and get a job and they didn't have the extra money. I was wearing hand-me-downs seven years out of style for school clothes.
Complain to the group chat monitor. Explain the problem without outright accusation (if you do, they may think you're the problem) and see if they can help you. That's what they are meant for. Ignore the brags about money - I have a younger brother who works three jobs, and brags about paying off his mortgage and "never worries about money."Sure, it's annoying - but he does it to get attention.I have learned not to listen when he gets that way.
