I a decent diffused Ring flash is the best idea for taking any texture shots. I got a hdd with around 40k textures now that I've collected over 5+ years mostly with my own camera.
If you can't get a good lighting set-up, you could try going outside on an overcast day since it's diffused light you wont get any harsh shadows or highlights. Could be a problem if you can't wait for an overcast day. If you are really desperate, maybe you could try early morning, just as the sun is coming up but isn't…