as far as investing in cold weather gear- you might laugh, but the first year I started commuting during the winter I went to the thrift store. I bought a wool sweater (a thinner but 100% merino wool sweater), a pair of wool pants, and an Old Navy down jacket (all at the Goodwill). I wore the wool sweater over a base layer and under my down coat and the wool pants I wore over my thin tights I already had. I was PLENTY warm and didn't even look too unfashionable. My winter commuting outfit cost a total of $14 and it worked for a whole season.
You don't have to spend a lot. The biggest expense I incurred was getting a good taillight ($25) and a good headlight ($40). I bought reflective 3M tape and put that on the spokes.

Anyway- just saying you can get by for pretty cheap if you don't need to have the top of the line gear.

And BTW, 2 seasons later I still wear that down coat and the wool sweater for my winter commutes. I have a pair of really thick tights I wear now instead of the wool pants. But I still think the wool pants were warmer.