Start things off with some sharp-cut tailoring. Take this River Island blazer, for instance; it's classic and adaptable, but comes with an unexpected twist - the lining is spectacularly jazzy. Pull on some black skinny jeans and a white shirt to go with it, keeping things relatively upscale without looking too flash.
Lastly, inject your outfit with the odd idiosyncrasy, like a colourful pocket square or tie pin. This lets people know you've got a personality without having doing anything silly, like wearing a full white suit. The shoes, of course, should be smart and understated. This Paul Smith pair is a strong choice.