You will require waterproof jacket and trousers. Essential to keep the wind and rain out and the warmth in. For the majority of Scottish winter activities I prefer a hard wearing set of waterproofs that will cope with the rigours of Scotland's winter season. I prefer trousers with at least a half length zip to ensure that they can be put on over boots.
Do not underestimate Scotland's winter climate. Think onions - lots of layers. This means you can easily regulate your temperature depending on what the weather is doing and how hard the conditions are at the time. Any kind of wicking fabric is recommended and cotton is to be avoided at all costs. Trousers which can dry out fast are a bonus.
Hats and gloves have a habit of either flying away or getting wet so I always carry a few pairs of gloves with me. At least one pair of thin gloves that I will walk in with and then a big pair to change into throughout the day - make sure that you can actually do things wearing these. I'm also a fan of a neck gaiter which can be pulled over my face when it's blowing a gale.Odlo
do a very thorough range of thermal underwear and Outdoor Research
have everything from shells, soft shells, loft, technical sportswear, hat, gloves and gaiters.