For a goofproof relaxed option, you can rely on this combination of a short sleeve sweater and charcoal skinny pants.
Charcoal Skinny Pants with Short Sleeve Sweater Outfits
The versatility of a short sleeve sweater and charcoal skinny pants means they'll stay on permanent rotation in your wardrobe. For something more on the classier end to complete this outfit, complement your outfit with a pair of black leather pumps.