There are a lot of things to work on.
* Palette: the last tree you posted has 20 colours (if i'm counting right). But they don't feel like that.
* Shape: the are a lot of things to work on the shape of the tree, look more references.
* Shading/Highlight: light and shadows are not just: if light comes from the right, i got shadow on the left. The give away the texture of the object and the volume. Your tree is still very flat.
Here's an edit I made:
I started making the edit before you posted again, then you had a smaller palette, but even then it wasn't very right. You had some colours that were TOO similar.
Hope it helps