This laid-back pairing of a blue denim jacket and a white crew-neck t-shirt is a surefire option when you need to look dapper in a flash. And if you need to effortlessly up the ante of this look with a pair of shoes, why not complement this look with dark brown leather casual boots? A great example of transeasonal style, this getup is ideal this spring. When it comes to casual outfit ideas for 20-something gents, this ensemble is perfect.