Rules I use as a geologists. No cotton, go for wool or wool mix. Avoid jeans. Leggings and craghopper fleece lined trousers are good. Smart wool full tog socks are excellent. Use lots of light layers to trap warmth. Good walking boots i go for leather and keep them waxed. Waterproof and windproof jacket and waterproof trousers are a must.
Getting a little bit excited now!