For an off-duty getup with a clear fashion twist, you can easily rock a white crew-neck t-shirt and charcoal chinos. Make black athletic shoes your footwear choice to avoid looking overdressed.
Black Athletic Shoes with White Crew-neck T-shirt Warm Weather Outfits For Men
If the situation permits casual city styling, consider wearing a white crew-neck t-shirt and black jeans. And it's amazing what a pair of black athletic shoes can do for the look.