I bought some ski bibs on sale 12 years ago. I don't know what they're made of. They still fit and they keep me dry.
I wear Sugoi sub zero tight underneath. A SAC buy.
I got my coat at an end of season sale at Target. I think it's by Champion. $25.
Downhill or XC, it's pretty much all the same. If you can't keep moving, keep drinking peppermint schnapps
The main thing I'd be concerned about is good gloves. Fingers frostbite easily.
2008 Trek FX 7.2/Terry Cite X
2009 Jamis Aurora/Brooks B-68
2010 Trek FX 7.6 WSD/stock bontrager