Slippers with REALLY thick foam soles. Mine are about 4cm thick. They're cheap faux sheepskin mules, but they're warmer than my much more expensive sheepskin boots that I had, due to the thickness of the sole.
Layers!! I know that PP have said this but a thin camisole layer that MUST be tucked in. And two layers on your arms... so either a long sleeved shirt with a jumper over, OR a long-sleeved poloneck with jumper over. Also a thin gilet. And maybe a big hoodie or simmering over the top.
Wool wherever possible if you can tolerate it.
Something at your neck whether it be a polo neck, buttoned up collar, or thin scarf or snood.
No gaps between your socks and trousers.
Hot drinks, even if only hot water (you get used to it!).
Going out for a brisk walk actually really warms you up. Vigorous housework also warms you up... scrubbing the bathroom and vacuuming are my go-tos.
But also keep the fabric of your environment as warm and well-aired as you can, by whatever means you can afford.