Well, right now I’m rebuilding my kit. My field backpack was stolen at the beginning of September. Aside from that, though…
Hat: wide brim, the wider, the better. My usual summer / gardening hat would have looked at home on the 1st Class gangplank of Titanic in 1912. It needs some TLC after 10 years, though, so my current is a really neat cotton crochet of similar style, in army green.
T-shirt: usually some form of nerdy. Lots of black (go figure), but I like to mix it up. I also pack a lightweight long-sleeve button-up (cotton or linen) if the weather is predicted to be anything other than sunny and warm. Since getting caught in a rainstorm while on the trail up in the mountains, a rain poncho and water-resistant camera bag are being added to the mix.
Jeans or loose linen trousers. Emphasis is on easily washable.
If it’s cold or really muddy, I have an absurd number of pairs of boots. Otherwise, I default to sandals; usually one of the pairs that I picked up while working at the local Renaissance Festival.
In the backpack: more water than I think I’ll need, protein shake, protein or fruit & grain bars, peanut butter crackers*, bottled coffee (I was practically born in a coffeehouse, therefore it is a food group), compass, magnifying lens, binoculars, spare batteries, spare camera, extra memory cards, fingerless knit gloves, maps, my national parks pass, sunscreen, bug spray, hand sanitizer, and bog roll. (I can usually find a porta-potty, but I never trust to it being well stocked. Also useful as emergency lens cloth.)
*The vindictive part of me hopes that the jerk who stole my pack is violently allergic. I tell myself that nobody deserves that … and then I look at the police report, listing everything that was in my backpack—backup / macro camera with multiple photos on the card, spare SD cards, binoculars, compass, magnifying lens, parks pass, the perfect pair of knit half-finger gloves, aluminium water bottle that was a gift, plus other odds and ends—and I start thinking that maybe anaphylaxis isn’t too much to ask after all.