Here's a link about value studies that seems decent:

http://davidmkessler.com/blog/23789/value-studies-the-artists-essential-tool

There's also a bunch of folks doing them in the daily sketch thread, if you feel like browsing that for a while. Putting color on top of a value study is actually rather easy, don't worry about that.

When stuff starts to look worse as you go, that's when you're learning! We all know how hard that can be, but it's a necessary evil. Basically, before that, you're too bad to notice how bad it is. As your skill increases, you start to notice how bad everything looks, but you're not good enough to fix it yet. Then after practice, it becomes possible to fix those issues. You're super happy about your art, until it starts looking bad again. Repeat.

Without this cycle, learning is impossible. People who are content with their art tend to be stuck and hardly improve. People who only see their art as bad have the same problem. You need the cycle. Notice that "bad" and "good" are relative terms. Most artists that are highly praised craftsmen still go through this cycle (though it slows down of course, but that only makes the "I'm bad" parts longer) and their "bad" is different from your "bad", but it might be possible that neither of your "bad"s will be perceived as such by a large audience.

As for the background, the problem is value. If you blur this and grayscale it, I will have no idea what I'm looking at. Throw the colors out for now, forget the architectural details, just try to make a grayscale mockup of the general form you want, using a large brush. Then you start refining. Right now, the mountains are higher contrast than the building for example, so I have to strain my eyes to pay attention to the building.

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What do you mean by "tile work without tile support"?

Try Pyxel or Pro Motion.

Here's an example of creating tiles in Pyxel.
Keep in mind the way he's building them is not a very good process.
It's better to create a rough scene and then break it down.
But it serves as a good demonstration.

I want to make you aware of these other options because not too long ago I didn't really care for tile work.
I'm a complete beginner when it comes to environments, entirely because I found the process to be very... blah.
Maybe you have a similar story and that's where a lot of your time sink and frustration is coming from.

Using Graphics Gale, it felt like a hassle to keep all my tiles in the scene up to date.
I would quickly get bored with copy pasting new versions of tiles already in use.
Example of me getting bored and dropping out once things started to expand on Graphics Gale.

After learning Pro Motion, I find tile work to be a lot of fun.
I can draw on large areas or small portions and everything is updated automatically.
This allows a lot of freedom to be creative and work on a bigger more scene complete scale.
Example of me having fun and building a much fuller image on Pro Motion.


Alternatively you could use Smart Objects in PS to achieve a similar work flow.
But I find it to be not as smooth.

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but I want people to see this and go "Holy crap that looks incredible."

Yah, dial that down a bit.
Don't let your passion bleed into expectation.