Some advice on how I could improve this outfit?

What the title says.

Also I need help with two more things:

1. Is the waistcoat too small? For some context the last button is at my bellybutton.

2. Is it too much for a school party-thing? For some context my class won’t be the one graduating. I think most people will wear button up shirts, but in my old school some people wore suits.

sorry for the pictures, I’m bad at taking them :”)