The outer layer, or third layer, is your protection against precipitation and wind. So it is important that your outer layer is wind- and waterproof. To avoid getting wet from the inside, it is also important that your outer layer is breathable. This seemingly opposite combination of functions is possible by using a special type of membrane, such as Gore-Tex or Dermizax. Jackets and pants with these properties are called hardshell. Are you in a place where it doesn't rain? Then a water-repellent jacket might also be an option. These jackets are windproof and breathable but not necessarily waterproof. Are you going fishing or birdwatching? Then breathability is less important and you can also opt for a jacket that is non-breathable but water- and windproof.