Have you tried the gilet over a dress? I often wear mine that way paired with tall boots. I think it looks great that way. The other combination I like is with trouser style long pants. The line of those pants seems to work well with the classic cut of the gilet. My long down puffer fits over my gilet, but it’s hard to know what the weather will be like right? It’s starting to get warmer here. I returned from a vacation in Florida and discovered temperatures had gone up above freezing and almost all our snow has melted.
I have been to so many graduation events. 2-3 a year for the past >20 years. The biggest impact will come from what you are wearing from the waist up. That is what people will look at and remember.