Too much noise! Try to reduce color count and smooth things out some!

I'm following some image as reference and the dirt has a lot of noise.
It was not the image I use but it's very similar:
Spoiler
I wasn't thinking to make something flat, but I'm gonna try to reduce the color count and noise, and see what I get. Thank you.

Hello everyone! I'm new here and I've been studying pixel art for a few weeks.

I'm thinking about begin a project of a survival game, and I'm starting by drawing the resources of the game.

Here is my first three resources:
dirt, stone, wood



(I'm not sure if its called "dirt" in english, because I'm not that fluent, but it's gonna be a resource to mix with water and make clay)

Do you guys have critiques to do that can help me improve these icons, or are them good?

I see no ghost here.. Try to draw its line art first, after you get a good drawing of a ghost, you start to think about shadowing.

Some ideas?

She seems cross-eyed to me.
I have the impression that that blue pixel is the color of her left eye (I know that it's the make up, right?), and it seems a little higher, making she looks cross-eyed, and one eye of each color.