If the setting allows an off-duty look, you can rely on a light blue horizontal striped crew-neck t-shirt and navy jeans. Avoid looking too casual by finishing with a pair of dark brown leather boat shoes. This getup should clear any doubts you had about dressing casually as a gentleman in his 30s.
Navy Jeans with Dark Brown Leather Boat Shoes Outfits In Their 30s
To put together a casual menswear style with a fashionable spin, consider wearing a blue denim jacket and navy jeans. On the footwear front, this ensemble pairs really well with dark brown leather boat shoes. A cool, less conservative pairing for a maturing gent.