Keeping your head, feet and neck warm is a great help. Plain wellies are a disaster as the soles are so thin - I wear Muck Boots which are heavy but cosy, or winter walking boots, plus woollen socks.
If there's any amount of wind, I wear a long windproof jacket on top of a fleece - those silly short bum freezers are a waste of space. I wear a fleece lined Buff round my neck and over my nose (discussed elsewhere on TAS) -plus a normal scarf, and a big thick Norwegian type hat with ear flaps. If it's snowing a blizzard I wear ski goggles
Gloves are a problem for me as my peripheral circulation is shot, so if I'm not going to be doing mucky stuff then I wear electrically heated gloves, plus thinner liners - the batteries don't last long, but I'm going to try rechargeables. When I'm doing mucky stuff and have to wear thinner gloves, my hands are soon in agony.
Under that lot I wear wool, wool and wool. One of my two vests is wool, the other synthetic, thick cotton knit shirt, then one or two chunky jumpers (hand spun
and hand knitted
from my own cosy sheep of course).
For my legs, I currently wear leggings, normal trousers and fleece overtrousers, plus waterproofs if it's wet, but woollen tights also work well as a base layer, or long johns as Mammyshaz says.
And again, keep doing stuff, as standing around is bound to be colder than working.
Just as well I'm not bothered with looking glamorous