FIRST LAYER CLOSE TO THE BODY
It must be warm, but must also allow perspiration to escape, which unfortunately cotton does very badly. It is therefore preferable to opt for cotton/synthetic mixes.
I have a big preference for the Heattech line from Uniqlo, and I'm talking about both the t-shirt line and the pantyhose line, which become extremely useful below 5 degrees. (although you're bound to look much less presentable when you take your clothes off).
The Hetteach lines are available in several sizes: stick to the first two if you're in town. Unless it is regularly freezing. The warmest range is however very useful in the mountains.
THE SECOND LAYER: IT RETAINS THE HEAT EMITTED BY YOUR BODY.
The idea of the second layer is to retain as much (warm) air produced by your body as possible. Because of its thermal properties, wool is the most suitable for this because it retains heat well thanks to the mesh of the sweaters.
You will find below a selection of wool
On top of the sweater, you can also opt for a tweed blazer or a vest. In a casual outfit, I have a big preference for the combination flannel shirt + big knit sweater:well-shabiller-winter-layering-2
LAST LAYER: INSULATING
For the last insulating layer, you can choose either a technical piece (parka, windbreaker, down jacket) or a more urban piece (wool coat or leather jacket). The first will be more suitable for very cold weather, and will in any case be the most suitable in case of heavy snowfalls. Here is our advice to choose your coat among our selection.
A large leather jacket can be a good choice (we have prepared the ultimate guide to leather jackets to help you find your way).
THE LINING AND THE SHAPE
For this piece, we adopt the same logic as for the body: namely a layer that will maintain the heat (preferably wool, cashmere or possibly silk which is also a good thermal regulator) and another that will insulate elements (often rain or snow).
This is why of course leather gloves are lined, and woollen gloves are often insufficient, except in dry cold weather.