Essentials? A three sided shelter where they can get out of the elements. On ours we have a pole we can slide across the open front to block the horse from coming out during thunder storms. Fresh, clean water. Many horses slow down drinking when it first turns cold which can lead to an impaction colic. They make tank heaters which keep the water about 40*. Plenty of hay. Forage (grass and hay) is what keeps a horse warm in the winter, not grain. I would not blanket unless absolutely necessary. Blanketing is an art. If the blanket is too light for the weather all it does is pack the hair down which means the horse loses its natural insulation. If its too heavy, then they sweat which makes them cold when things chill again. The only time a horse needs a blanket is when they are old enough that they are expending more energy in keeping warm than they are taking in calories. There are plenty of "can do" steps but those are the necessities.