Setting the shutter to 360° gives you one stop more light, faster lenses with f/2.8 or less will help.
But ultimately you will need light, so best advice is to invest in some portable lights and learn how to use them to create a moody scene. Using lights is the biggest and most important improvement.
If the person you are shooting is moving then you need an assistant moving the light too. (A Chinese lantern on a pole for example).
If you are shooting a talking head lecturing then you will need some light too. Maybe one on each side or from above.
Finally you can use the higher ISO stage from 1250 on for less noise in the shadows (but with less dynamic range) and some in post denoising.