A black crew-neck t-shirt and khaki chinos are totally worth being on your list of menswear staples. Ramp up this outfit by wearing dark brown leather work boots. Keep this combo in your front hall wardrobe when warmer days are here, and we guarantee you'll save a ton of time brainstorming for an outfit on more than one morning. When it comes to casual fashion tips for gents in their 30s, this outfit looks cool on almost any gentleman.