The layer with the circle should be behind the female.
The backgroungs should be a color that looks best like the camo you will use the image on (for blending), often that is grey.
If you have all layers visible and it looks OK in GIMP, then you should be fine.
Save the image as BMP. Make sure it is 256 colors/8 bit, eighter directly in GIMP of by converting with Bright afterward. View it in game.