I do tons of thrift shopping so I have this down to a science.
I wear - my best fitting bra and knickers, black leggings, a tight black camisole. Layer 1
Pants that are easy and fast to slip in and out of, I have a pair of dockers I like for this, a comfy, but dressier top, usually a long sleeve u neck jersey top that I quite like, it's black and gray sort of tie dye - Layer 2
If it is absolutely freezing I wear a charcoal colored cashmere cardigan. Warm as can be, but also light and easy to toss in my bag. I usually wear a pair of black slip on Chuck's. That is Layer 3
I carry a cross body canvas bag that can sit on the floor or hang from a hook and leaves both hands free. It has to be a bag that the phone, keys, etc can go in, because if you are taking your pants off and on, you don't want to be dropping those things.
I also carry a small tape measure, a set of screw drivers (I know, I know) a magnet, a small magnifying glass, a flashlight, a tablet (a tiny one), a pen, a swiss army knife and lots of small bills and change.
Whew! Is that a good list or what?
I am always looking for stuff I can pull apart and use in my jewelry, so I need to be able to see if things are gold or silver, plated or not. I am also still furnishing our apt so that accounts for part of those things.