I tend to use thin layers also. I have ridden all the way down to the mid 30s with bib shorts, leg warmers, full coverage booties over my shoes, an underarmor long sleeve lightweight shirt under a normal jersey, covered by a lightweight PI jacket, with full finger gloves. I usually wear a band type ear warmer, but find i don't like much else on my head other than my helmet as it tends to cook me too much if I do.

I am currently looking into some decent bib tights instead of the shorts and legwarmers combo, but haven't settled on the ones i want yet.