Why do you think you need a vest? Everyone here is kinda making jokes but seriously, what are you trying to achieve. Do you mean that you think to be seen as professional, you should wear a vest? You mean a sweater vest I hope and not a 3 piece suit. If you’re looking for advice on professional attire, I would 100% not ask all these nerds. I’ll give you my opinion but then it would do you well to google “professional attire examples” or something and review some ideas visually. My advice would be to start with some button down shirts and slacks. If you want to add a little something else then get a few v-neck sweaters to put on over them. Don’t buy way too many of anything cause you’ll have favorites and never wear others.