Consider teaming a henley shirt with black sweatpants and you'll be ready for wherever the day takes you. White athletic shoes are a nice idea to round off this ensemble. Casual looks for 30-something gentlemen aren't actually that hard, as you can see.
Consider wearing a henley shirt and black sweatpants to feel completely confident and look trendy. A cool pair of white athletic shoes pulls this ensemble together. This getup demonstrates that hitting 30 is no reason to shed casual style altogether.