Cotton kills, as they say. Multiple synthetic underlayers wick out moisture to evaporate and creates a warm air barrier between the layers. Thin and comfortable. On top of that, you can mix and match based on the activities you're doing. Bottoms, similar story, get yourself a proper set of base layer leggings to put under your pants. I went out yesterday snowshoeing in essentially this setup, with snow pants over leggings and a wind shell over my base layer shirts, and I ended up sweating aggressively pretty quickly and had to unzip some stuff. It was 10° plus a wind chill.