Spring/summer casual for the 40 year old is easy. In your case, the move from cargo shorts to lightweight chinos in light brown, white, and maybe other pastels if you want, will make a big difference. Polos are fine but be picky. Solids that contrast with whatever you wear as pants are always good. Short-sleeve button down shirts in madras, poplin, any weight of cotton or linen that you like, are good. Popovers. For shoes you might look at suede plain toe bluchers ("bucks") and loafers of the Alden leisure handsewn variety. They are a bit more neutral and versatile compared to boat shoes. A lot of my summer pants are by Hickey Freeman. They do chinos well in my experience. Otherwise everyone sells this stuff. Stay out of malls. Go into better independent men's stores when you travel--you are a pilot--and see what they have. And buy what you like. Don't be afraid to pay for quality. $100-$150 is not too much for a quality summer shirt that you love wearing and that looks good on you. Economize by purchasing fewer things. A small rotation of high-quality stuff you love is the way to go, especially with summer wear which can pretty decadent in terms of wearing pleasure. SF is a good place to learn about stores worth visiting when in you are different cities. Ask or use the search function. I think linen pants are more elegant, interesting, and cooler-wearing than light-weight cotton chinos. Besides, too many people do chinos. Be different. But ... I agree whole-heartedly on the white bucks and Alden loafers. I have both and they are very versatile and both have a degree of panache without the dandyism. I also agree completely on a small rotation of high quality clothes rather than a large collection of "meh" articles. You don't need more than six or seven pants per season or more than about a half-dozen casual shirts. Use the money you save by buying less but buying better. You won't regret it. Regarding brands, my baseline is Ralph Lauren. Everything else is measured against it re price point and quality. Sometimes I find better, but usually, I don't. But do splurge on the fresco trousers. Light and dark grey slacks are really versatile in the summer and they wear very cool.