Hi!! Based off of those two pieces, I would say high tier 4 to low tier 3 (40-60k). I love what you're doing getting into body prep and grounding. I totally see what you were trying to do with the stick in the second piece and I like that it looks almost like the horse is trying to turn and see what's poking him haha! And amazing job putting the horse behind the tree. As of right now, I think your biggest aspect to work on is shadows. You've got some awesome highlights with the moon shining on the horse's back and the sun rays illuminating the laying down horse, but you don't quite have the right corresponding depth of shadows. Particularly in the laying down piece where you can see how dark the ground is but the horse's legs are still rather light. Personally, I like to use layers set to Multiply and, in this case, I would use a dark green (pick a dark color from the environment, not black) airbrush and go over the areas that should be in shadow.
In regards to body prep, careful not to oversmudge against the direction of the horse's musculature. Looking at the bay moon piece, there are a few spots on the neck with stark, straight smudge lines that aren't as natural as the lovely softer smoothing on the laying down piece.
Last little tip: blending the horse into the colors of the environment. The laying down horse fits quite well but the bay looks a bit unnatural because its coat colors are vibrant shades of red and orange that don't seem as natural surrounded by cooler, muted colors. What I like to do is duplicate my background layer, Gaussian blur it completely, then set it to Soft Light and clip it above my horse layer. It makes a world of difference in naturalness.
Overall, you're doing absolutely amazing for your first two pieces!!! Way better than I did with mine (
click) haha! Can't wait to see what you make next <3