Man! That's looks awesome for using a mouse!
The Ember into Ashes map is on of my favorites ever, and I often try to replicate the style (mostly unsuccessfully).
I think if you want to make maps like this my advice would be, 1. Get a drawing tablet (if you can)
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2. Go through all of the tutorials on Fantastic Maps many times 3. Practice, practice, PRACTICE!
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Drawing tablets are extremely useful, and I would highly recommend getting one, if that's a possibility for you.
The background texture looks a bit low quality, but that's something you could easily fix.