If you dont want to look like the michellan man... you really need both the base layers and a quality outer. If you already have something to get you by for outer layer, its the under layering that is most important. On the coldest of days, I use 3 layers for unders. A very thin base, a medium, and then a heavy layer under my outer clothing. All should have wicking capabilities moving moisture outwards away from you. Nothing beats the trapped space between those layers for insulating properties, and still remain very comfortable and mobile. Most good layering materials avaliable today are very thin. Its all for not though, if you dont have a good outer to wear, that makes the under layers work trapping heat. Anywhere the heat escapes is draining the abilities of the layering effect. As said already, finish dressing at the stand. If you work up a sweat, you are screwed. Carry your outter and 3rd,or even 2nd layer unders...based on what temps you are dealing with.