This combination of a white crew-neck t-shirt and khaki dress pants is great for elegant settings. For footwear, go down the casual route with a pair of white leather low top sneakers. Wearing this, any 30-something guy will put most of his peers to shame.
Opt for a white crew-neck t-shirt and khaki dress pants to don a dressy, but not too dressy outfit. Ramp up your ensemble by wearing a pair of blue leather low top sneakers. As a 30-something Millennial gent, you want to start dressing more like a mature gentleman. In this case, inspiration like this proves very useful.