My clothing system for three season backpacking:
Short sleeved technical button up OR shirt. I like this as I can wear it when it's warm, it dries super fast, has a collar, and even looks okay...
I wear a spandex short as my bottom base layer. Keeps everything where it should be.
Then a zip-off synthetic (quick dry) pant.
Merino wool socks
In my pack:
OR Helium II waterproof breathable shell jacket. This thing weighs 140g in size M and is AMAZING. No pit zips or big pockets or other heavy features. Breathes about the same as Pac-Lite, and seems pretty durable. Mine has seen two hard years and is in great shape. Always in my pack now...
I have some full-zip Gore-Tex pants I also bring. Then, if it's pouring or super muddy, I use these gaiters. Super light, go on in seconds, and plain work. I didn't use gaiters for the longest time, then these very light ones starting hitting the market, and now I bring a pair.
My intermediate layer is the VERY breathable OR Radiant Hybrid Hoody. It's not the lightest fleece jacket, but really works well. I use it all the time, in all seasons. It's super durable. I love that in the cold of the morning, I can put this on and be moving and keep my temperature perfect. During ski traverses, this was an invaluable layer.
Then I have the classic Patagonia down jacket as my insulating layer. Combine the fleece and the downie, and I'm good fine while milling about camp in the morning or before bed. I can add or subtract the Helium as wind protection is needed.
Then I have two pairs of gloves. One a thin fleece glove that I can wear while cooking, etc. And then a heavier glove for the morning. And a touque and ball cap.
Sounds like a lot, but I use every piece on every trip, and it all works. Takes me from the cold of the morning to pulling hills in the heat of the day.
Other odds and ends I might take:
Spoon, knife, lighter/matches/fire-starter, first aid, sunglasses, sunscreen, bug spray, toilet paper, Pristine Drops, platy/nalgene, "night kit" (contact solution, case, glasses and spair contacts)
Then the big systems:
Sleeping/Shelter: Sleeping bag, pad, tent
Cooking: Stove, pot, mug (maybe)
For my three season Rockies bag, I use a -7C down bag.