Try improving the GFX, it looks like you made it in Roblox Studio, try to make the lightning more visible, and your watermark is too big, i recommend not selling the gfx with the watermark, remove the watermark and give it to the buyer, and put a small watermark in the corner when you share your work.
Your prices are too high, it’s basically a render that you made and sell it for 10x than it should be.
I got a really good gfx for 100 robux
(made by funleader179)
Try to make your work cheaper. The quality is a little bit bad, try to watch tutorials and in the future, you could sell your GFX for 10k Robux.