A white and blue gingham long sleeve shirt and khaki chinos will give off this casually stylish vibe. The whole ensemble comes together quite nicely if you introduce a pair of white canvas low top sneakers to the equation. If you're not sure how to dress as a 20-something, this outfit is a wonderful example.
For a look that's pared-down but can be flaunted in a ton of different ways, try teaming a white and blue gingham long sleeve shirt with blue ripped skinny jeans. You could perhaps get a bit experimental with footwear and add a pair of white canvas low top sneakers to the equation. Laid-back outfits for young guys aren't actually that hard, as you see here.