You don't need to spend a lot of money. I'm a big fan of a nice simple liner-less (3-layer) shell over an insulating layer over a long underwear layer.
The shell and long underwear never change. I vary the (or add an) insulation layer based on conditions.
The insulation I most often wear is the EMS Primaloft Jacket: http://www.ems.com/products/product_...1052372 76768
It's very warm, very very soft and comfy (Primaloft is basically synthetic down). Very versatile jacket, looks sharp, and is a great general winter use jacket by itself.
It it's a little warmer I'll wear the relatively thin fleece jacket that came with my old Columbia 3-in-1 jacket or a simple 100 weight fleece shirt I got at Wal Mart for about $15 a couple years ago.
As for an outer jacket, go to the local outdoor store and try on shells until you find one that you like and fits you well. Buy at the end of the season to get some great deals. Your local EMS will have some killer Mountain Hardwear and The North Face 3-layer waterproof/breathable shells in the neighborhood of $200. REI will hav similar products at similar prices.
The most important thing, IMO, is to have a nice shell, a nice synthetic long underwear top, and at least two insulating jackets of varying thickness that you like.