For something more on the relaxed end, consider this pairing of a shawl cardigan and a navy long sleeve t-shirt.
Navy Long Sleeve T-Shirt with Shawl Cardigan Warm Weather Outfits For Men
A shawl cardigan and a navy long sleeve t-shirt are essential in any man's properly balanced off-duty wardrobe. As for shoes, complement this getup with beige suede desert boots.