+1 for cheap inexpensive shell with layers underneath. I have an old shell that was like 25 bucks.

For temps around freezing, 3 layers underneath.

For temps well below freezing add another layer....or two if truly necessary (I have a wonderful Pearl Izumi vest that I break out when it's 20ish or colder).

It's really not rocket science.

I would avoid getting a thick jacket, the cheap shell is much more versatile.