Go for something stylish and timeless with a waistcoat and a navy and white dress shirt. To bring a more laid-back aesthetic to this getup, add a pair of grey leather desert boots to the equation. Also, it's a good getup to fit in with a professional crowd.
Solid proof that a waistcoat and a navy and white dress shirt look amazing when married together in a refined getup for a modern gent. If you want to easily dial down your ensemble with one single item, complete your outfit with olive athletic shoes. In your thirties, you want to start dressing like a grown-up. If that's the case, looks like this are a tested option.