A green crew-neck sweater and navy jeans are absolute menswear staples that will integrate really well within your day-to-day casual lineup. The whole getup comes together perfectly when you round off with a pair of brown suede desert boots. As you can see here, it's very easy to look amazing and stay warm when chillier weather arrives, thanks to this outfit. All in all, an ideal demonstration of semi-casual fashion for 20-year-old gents.