My boss does a sleezy that goes over the head and neck and then a sheet, insulator blanket, and a turnout blanket. She also put a neck warmer on the horses too. They have a shorter coat and are very sleek looking.
He is narrow at the shoulders but a little wider behind. So I was thinking one plain sheet, one light weight, and a medium. I was told that you should have two incase it gets wet. Would it be ok if lets say my medium got wet and the barn manager put the light on him until the medium dried?
When buying a blanket, bear in mind you should rug as if the horse had very little fur because the rug stops the horses fur from raising up and insulating him naturally, so putting a light rug on inhibits the natural heat regulation but doesn't offer much warmth.
For Alli, I have a 300gram (meby350) (10-12oz) rug, and a 200g (7oz) rug. She is thin skinned compared to other breeds but its only when it gets below freezing that I put the heavy rug on. I don't know farinhit, but I'd go a medium rug for anything around freezing and a heavy rug for anything much below freezing for a freisian :)
(I always try to go for rugs that are 600D + a theres nothing more irritating than finding a brand new rug with a slash the whole length of it the first night its on!)
ETA- it also depends whay the horse is used to. He may only need the heavier rug when its a lot below freezing.
I blanket my boy in a 1200D 150 gram of fill turnout blanket by saxton. However, it is kind of short on his big belly. You might want to go a size up if he's stocky. Also, make it has expandable leg pannels, so he can run around. I'd go with a 1200D if it all possible, because other horses in the pen might tear it up.
Maybe also look into getting shoulder guards. Its kind of like a stretchy jami for their shoulders and withers. It will prevent rubbing.