By layering a sleeveless knit vest over a simple t-shirt and loose slacks, you can successfully create a style that is both casual and elegant.
A cream button-up sleeveless knit vest is available from Arket.
Shirt: a white oversized t-shirt designed by COS
The trousers are black pants with broad legs by Everlane.
shoes: New Balance shoes with a chunky white tread pattern