For a winning smart casual option, you can always rely on this pairing of a red puffer jacket and black leather jeans. Rounding off with black leather high top sneakers is a fail-safe way to infuse a dash of stylish nonchalance into your ensemble. We promise this ensemble is the answer to all of your autumn style woes. If you're not sure how to dress as a guy in his 20s, this outfit is a fail-safe option.