Fair enough, I agree if the thread keeps going in that direction it won't be constructive.
A scrappy edit;
Firstly Ryumaru's comments still stand. There has been a bit of an improvement on the clouds, but you missed what he was saying about how they converge together.
Secondly you need to consider your light source, that's what the edit is showing. Assuming you are going with the light position elluded to by the tree, the light source is behind the tree and on it's right (That's not to say the tree doesn't still needs a rework of it's shading).
It might be worth doing some shading excercises. Try to shade a ball, and a whole bunch of other simple shapes. Once you understand that you can move that thinking on to amorphous objects such as the tree. This might help get you started.
lighting theoryAlso the earlier link,
.
Things not covered by my edit:
You need to put more consideration into your colours. From a realism standpoint, colours become more desaturated as you approach highlights and shadows. There are also rarely monotone shifts between one colour and another in real world situations as is portrayed with your colour selection. (see hue shifting on that earlier link).
That colour underneath the grass shadows doesn't make sense. It's barely visible and I don't know why you put it there as it doesn't really represent how light works.
Also your line's need a fair bit of work.
The grass (extremely) as well as the tree in some areas suffer from banding.
Don't bother with the dithering on the sky at this stage, get everything working together nicely first. Dithering is used as a final technique, usually either to add polish or to conserve colours.