That's really nice for a first composition!
Very nice ambience. And while I get that you were going for *dark* vibe, don't be afraid to experiment more with some lighter tones - it will help make the whole thing sound balanced and less muddy. I can hear some crystaly music box/celesta going on in the background at times, it wouldn't hurt to boost them a bit (both eq & volume). Maybe make things a bit more dry (reverb tails seem to clash at times). Very common practice is to get some sharp eq on reverb tracks (if you have separate, parallel tracks for effects, which you should) to get rid of the very lows and very highs, as they are usually unnecessary on a reverb. In a similar vein, some more eq work to remove lower mids would be nice, to enhance the clarity.
I guess that in general my best tip for you would be to strive to "enhance the clarity".
Then maybe some more variety: shake things up a little, throw in a celesta/bells only interlude/bridge, into some B part, take us places! The track is nice, but it really could've been half as long and still tell the same story.
Another cool thing you could do is to play with dynamic panning - it works wonders in such ambient tracks. You can make the plinks and plonks appear semi-randomly around the listener, or make your pads gently flow from side to side. It's those little things that make such tracks extra interesting.
Sorry for the wall of text, but you called for a feedback and tips, so I threw everything that came to my mind at you :) If anything sounded a bit harsh, it wasn't my intention :)
Good job, keep making stuff!