I'd say middle tier 3. I would work on making the horse look a little less grainy and pixely if that makes sense. I would also experiment with hair painting, making your hair more flowy and natural :)
i just want to help you with some stuff:D when grounding in grass try to use a fading eraser or something like if you use ibis paint the the particle airbrush on half opacity and with grounding on solid ground draw a shadow around the bottom of their hoof and guassian blur it on what makes it look natural:)