What I wear (in relatively warm weather): long-legged pair of biking shorts (baggies), t-shirt of some sort, wool socks (Smartwool or similar); a pair of so-called "approach" shoes that happen to have flat, stiff soles that seem to mate well with the pins on my platform pedals.
The shorts I have are made with longer legs to accommodate shin pads worn by freeriders. I'm not a freerider. I just prefer to have less of my leg showing. Trust me. That's a good thing.
In winter, I dress more warmly. You'll often find me in: base layer top and bottom, either jean pants or cross-country ski pants, windproof fleece jacket, hiking boots, wool socks.
What I currently carry for most rides: hydration pack full of water, combination shock/tire pump, tire levers, multi-tool that includes a chain tool, couple of snack bars, extra set of disposable contact lenses, lubricant/rewetting drops for my contacts, extra tube, tiny set of probably useless tire patches, alcohol-based hand cleaner, small pack of tissues, whistle, cell phone, a handful of Halls Fruit-Breezers if I have some. (I really need to add a bit first-aid gear to the mix).
For short rides of only few miles, I might not bother with anything but a water bottle. I hate carrying stuff, but on long rides I will carry what I need in case something happens. I'll even go with a larger pack and more supplies if I feel I might need them. It depends upon where I'm headed and whom I'm with.
Protection gear: helmet; gloves; sometimes sunscreen and/or bug repellent. My riding doesn't really call for shin pads, elbow pads, that sort of thing. Although I will say that crap happens, and elbow pads would've been welcome the last time that I crashed badly (onto a crushed stone trail surface).
First-aid gear: It's been on my mind to grab a couple of 5x9 combi-dressings and a roll or two of conforming gauze bandage.