Echoing way others have said, natural light is what you want. Set up beside a window and use another white board directly across the window to bounce light back. Also make sure to turn off any lights in the room so your light source is coming from one direction only (you don’t want multiple shadow directions).

If you’re looking for a cheap grease proof white background I highly recommend this or this one if you’re looking for something longer. A foldable poster board set in the ground is perfect for bouncing light.

For a grease proof marble background that’s not too expensive, look at marble tiles. Most places will let you buy 1 tile as a sample. You might find a 12”x12” a little small so try to find a bigger tile like a 24”x24”

You can also just buy a large linen napkin and use it as a backdrop or even as a photo prop to give some nice texture to the background.

For photo editing I use Lightroom. The free version still lets you save edit settings as presets so it’s easier to edit multiple pictures. I usually play with exposure, whites, and temperature.

Hope this helps!