The key to staying warm in cold weather is to stay dry, prepare for the temperature, and keep the wind off.
Bra/Underwear (non-cotton)-snug boxer cut bottoms are great for winter for men and women. Men can also purchase a pair with a lovely windproof panel in the front.
Next-to-skin, base layer, wicking fabrics must be non-cotton. You can use a snug technical tee shirt or long sleeve depending on what you will be using for your insulation. There are a lot of great options that include wool, seamless and other soft synthetics.
Middle layer for warmth (still non-cotton). This could be a long sleeve top worn over the short sleeve base layer or a running vest (see pic above) thrown over the long sleeve base layer option. For pants, you may choose either a winter tight or looser running pant. Another popular option is a 3/4 tights for temps in the high 30’s to low 40’s.
Shell for rain, snow or wind. Some people prefer a lightweight shell over thicker base and insulating layers, while some folks like a thicker jacket on top of slimmer layers. Either method work well. Vests work well in this category also.
The Head: An ear band is sufficient for temperatures over about 25 degrees. Snug hats are recommended for cooler temperatures in order to help keep heat from escaping through the head.
The Hands: This is one of the most individual pieces out there. Some runners are great with thin and others need thick fingered gloves with the mitten pull over. If you have hand numbness circulation issues, then putting hand warmers between your skin and gloves works great!
The Feet: Wool socks are available and recommended.
Investing some basic winter running clothes will pay warm dividends for many years to come. Quality clothes will easily last 5-6 years and many times, much longer.
*Some pieces of clothing combine layers to reduce bulkiness and enhance moisture management.