Well, it depends *very* much on what I am doing, and what the temperature is.

Have a look at my usual gear list linked through my signature and you'll tell something from what I am carrying "three season" - but basically, in non-winter conditions, I usually wear a synthetic boxer brief type undershort and a pair of convertible pants while hiking. on top I start with a synthetic T shirt. As I am moving, and active, typically I will only put over that possibly a merino wool long sleeve shirt. and/or a 100wt fleece in the event of rain, and a windshirt - top it off with a poncho if it gets really ugly. This is enough when it's reasonably warm out and I am moving. When I *stop* I put on a midweight long john bottom, possibly under the pants or by itself, and then layer up with another wool shirt (I always take two) and an insulating layer, usually a primaloft pullover.

Winter's a bit different. I'm always wearing a base layer of
a synthetic mid long john bottom, and the T and two merino wool shirts. On top of that I typically layer in cashemere sweaters and fleece. I get cheap as dirt "old man" cashmere sweaters at the second hand store. If it's brutally cold am usually moving in a pair of heavy wool pants with suspenders,
often then only layered up with the above base, one or two sweaters (more if it's colder!) and an anorack type jacket overtop. When I STOP in winter, I change out into unsweated 300 wt fleece bottoms with shell pants, a new fleece as needed and then a big ol' down parka. I don't walk or move in down because I will sweat it and myself to death.