I have all of the things you mention, because there is a purpose for each at different temperatures. And, it takes a lot of experimentation to find out what works for you. Arm warmers, knee warmers, and leg warmers are cheaper than other stuff, and also come in all kinds of "thickness" and materials. I cover my knees below 65. Like you, I'm short, so knee warmers work for me as almost leg warmers. But, they are light weight. I also have one pair of knickers; regular road cycling knickers. I guess I wear the knee warmers and knickers when it's below 65, down to about 50-52, depending on cloudiness and wind. Below that (and sometimes above, given other factors noted), my rear gets cold and I wear medium weight thermal tights over my cycling shorts.I also have a heavier pair. I have sleeveless, short sleeved, and long sleeved base layers, long sleeved regular, light thermal, heavy thermal, and wool jerseys. My top heats up pretty quickly, so I like to have many options for all weather. I have a wind jacket you can wear over anything, a winter jacket for really cold temps, and a Showers Pass rain jacket. I don't purposely ride in rain, but I mostly have it for touring. For my head, I have some really light beanies, a couple of buffs, and one thermal one and one really heavy thermal one. Two balaclavas. I mostly wear wool socks all year round, so I have a lot of those, as well as toe covers, booties, and 3 kinds of long fingered gloves.
This sounds like a lot, but I've accumulated it over the years and I've also extended my riding season to pretty much until there's snow on the roads, or the roads are just too crappy with salt, etc to ride. Also, when I first started riding in the cold, I used a lot of my x country ski stuff for my mid layer and I already had the base layers. Some years I don't ride at all in January or February, but most years I get in a couple of rides, in between the x country skiing.