For an ensemble that's super simple but can be flaunted in a myriad of different ways, dress in a navy and white print long sleeve shirt and a grey crew-neck t-shirt. Finish with a pair of brown leather chelsea boots to punch up this ensemble. As you mature into your 30s, you want to start dressing like an adult. If that's the case, combos like this are a tested option.
A navy and white print long sleeve shirt and a grey crew-neck t-shirt are great menswear staples that will integrate brilliantly within your casual arsenal. You could perhaps get a little creative with shoes and complete your outfit with grey leather chelsea boots. As a 30-something gentleman, you want to start dressing more like a mature gentleman. If that's the case, inspo like this comes in useful.