A navy and green plaid long sleeve shirt and navy jeans paired together are a match made in heaven for those who love relaxed combinations. If you wish to effortlessly elevate this ensemble with one single piece, complement your ensemble with brown leather casual boots. While it can be a bit of a challenge to stay on-trend on extra cold days, it's combos like this that prove it's quite doable. How's that for style inspiration for 20-something classic and casual dressing?