You will require waterproof jacket and trousers. Essential to keep the wind and rain out and the warmth in. I prefer trousers with at least a half length zip to ensure that they can be put on over boots.
Think onions - lots of layers. This means you can easily regulate your temperature depending on what the weather is doing. 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.
I carry a thin pair of gloves and a wooly hat with even the best weather forecasts. A sun hat is a good idea on those hot and sunny days.
I use short length gaiters in summer to prevent my socks looking like a heather bush.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. Their attention to detail is excellent and have a very extensive female range.