Just returned (jan 19, 2024) from an 18 day expedition to the Falklands, South Georgia, and Antarctica peninsula with Polar Latitudes---fantastic!! I had just the right clothes..mostly polyester fleeces of various thicknesses, mainly bottoms. I had medium and a thick thermal tops and wore thin layers over. ALWAYS warm enough. Got most of them from 32Degrees online. I had thick polyester socks for the muck boots (no need to get boot inserts--I tried them, and they made the boots very tight) along with thinner socks that I wore under those. I had 2 outer pants to wear on he zodiacs and landings---an old pair of ski pants and some water resistant hiking pants. Wore fleece under them.
The weather was marvelous and not that cold. South Georgia was probably 35-40, and Antarctica was around 32-35, but we had SUN!!
One thing that I would recommend is a goggle that is close-fitting on your face to use as a windbreak and sunglasses when you are on the zodiacs--I do not mean big ski goggles. They are smaller and have an elastic band for the head. Great addition for me! I took along mittens as well as finger clothes. I also had underarmour glove inserts (that let you use a phone camera) that worked well. What do I wish I had brought that I didn't--my fleece gloves that I had left at home.
Don't bring any cutesy, dress clothes--everyone is wearing their zodiac clothes generally, or jeans, or just informal stuff.