A black print crew-neck t-shirt and brown cargo pants are absolute staples if you're putting together a casual wardrobe that matches up to the highest sartorial standards. Tone down the dressiness of your ensemble by rounding off with athletic shoes.
When the setting allows casual street dressing, you can easily wear a white crew-neck t-shirt and brown cargo pants. Go off the beaten track and shake up your look by wearing a pair of athletic shoes.
When the setting permits an off-duty getup, marry a grey crew-neck t-shirt with brown cargo pants. You could perhaps get a bit experimental with footwear and tone down your getup by rounding off with a pair of athletic shoes.