I generally hike in the Uintas, which are fairly similar to the wind rivers. I carry a set of midweight fleece long underwear, a nylon, long sleeve hiking shirt, a fleece jacket, and a poncho. 90% of the time I have the nylon shirt on with a t-shirt undershirt (not cotton). In the mornings I wear the fleece long underwear top and the nylon shirt. Sometimes, I put on the heavier fleece jacket. I haven't been cold with all those layers on. My next line would be to get under my sleeping quilt.
Fleece is heavier and bulkier than down or other synthetic jackets. But, it dries VERY fast and is almost bullet proof. Yes, it can melt. But sitting next to a fire with sparks just gives it a few more holes. My fleece are all cheap thrift store finds. The wind blows through them. A few more holes doesn't hurt it.

Personally, I think newbies are better served with fleece than with a down jacket. You need some experience to keep your down dry.
Sometimes it is more comfortable to walk in the rain with a fleece jacket (and just let it get wet) instead of a rain jacket. Kinda like the difference between waterproof, and non-waterproof fast drying footwear.