If you are new to clipping horses, you want to choose a blade that is forgiving and won’t leave lines on the horse’s coat. A good choice might be an A2 blade, or a medium blade that leaves approx. 2.5mm of hair. Anything too fine can be difficult for beginners.
You can always start with a medium blade, and re-clip with a fine blade as you build confidence.
Clipper and Electric Fencing Specialist