You've gotten some good advice, and I'll add a little to it. First, layering is good, but make sure you layer with the right materials. I've hunted from the Lincoln NF of New Mexico, to the plains/hills of NE Missouri and the mountains of NW Montana, as well as haviing some experience in the Chihuahuan desert. Leave any cotton you have at home, period. Some will disagree, but better to have only a few changes of the proper material than to have to change several times due to the wrong materials.

Base layers of polypropolene, or similar wicking synthetic are good. Look at using synthetic heavy socks, or wool, over a polypropolene sock (Walmart is now carrying these in this neck of the woods and prices are reasonable). Next is up to you, but I prefer a wool trouser on my lower limbs, others recommend a fleece layer and some type of water proof outer shell. I overheat easily and tend to prefer to wear things light (I mostly still hunt) and carry a fleece insulating layer to add later if I decide to make a stand. Up top I layer with polypro, then fleece, then typically either a wool vest (for down to around freezing) with a wool hat, or if colder and windier I add go with a fleece shirt and a wind blocking pull over with fleece outer and gore-tex type (I gravitate towards the generics, they seem to work as well for me) liners.

I'm going to try some of those ear warmers that you wear like a headband with ball caps this year for my ears, but usually wear either a wool hat (when still hunting) or wear a fleece balclava when making a stand. Even with the wool I'll wear a mesh face net while still hunting and that has worked well. I also wear polypro liner gloves still hunting and fleece gloves on stand.

Depending on where you are from, the relative temps in SE WA may be higher or lower than what you are used to. Coming from MO with high humidity this mountain country is not nearly as cold with like temperatures. HOwever, now that I am used to it, returning for deer season to MO means I tend to wear heavier clothes as the high humidy chills me faster.

As to coats and parkas, I reserve those for 0 and sub zero temps for predator hunting. I prefer layering as I find that I can shoulder a rifle and pack easier than one heavy coat.