My sales have been up for November and December, but I've only been open since June. I've been working at building up my inventory, though, since everything is handmade and takes a while to make. And I also made a goal to increase my shop views during winter break while I had time. I think those two factors, coupled with Christmas, have helped me go from one or two sales a month to about five.
Also! I've been keeping track of listings that get a lot of favorites/sell out quickly and I've made an effort to create listings that are popular, so basically just working at knowing my target audience. My "That Shit Cray" pillows always sell out pretty quickly, so I made a listing where people can order custom-made pillows, instead of cranking them out at random. It's been a hit!