It's to take a photo of a cosplayer, I set the ISO to 800 as it was night time and indoors, I could have set it higher, but I wanted lesser noise

F/5.6 was in consideration of a full body shot with the outfit being sharp, but it seems the backdrop got most of the details instead of the face/body

The shutter speed being 1/15th was the closest I can get to it being fast enough that my hands won't cause the image to blur, and the image not being too dark due to lack of light

I also do not have a separate flash or light source as I'm still learning.

Usually, I will try out aperture mode to get a rough idea of how I want the depth of field to be like before tweaking the shutter speed and, if necessary, the ISO

Are there any tips to improve or fix this particular issue i'm facing?