This pairing of a multi colored crew-neck sweater and blue jeans is super easy to do and so comfortable to rock throughout the day as well! For maximum impact, complete this look with a pair of brown leather casual boots. So if you're on the hunt for an outfit that's on-trend but also feels totally spring-ready, this one fits the task well. And if we're talking casual outfit ideas for gentlemen in their thirties, this getup is a good look on almost any gentleman.