My advice would be to prepare yourself for Mother Nature. Horses need care regardless of the weather. There will be times when you will have to go out in the torrential rain, sleet or snow, or the bitter cold as well as the sweltering heat. None of which are an excuse for not performing your duties for your horses. If your horse is in a stall, that horse depends on you for everything, and they need care every single day. If they are in a pasture, they may sometimes need to be brought into stalls because of severe weather, and it is up to you to go out into whatever horrible weather there might be and bring your horses in where they will be safe. Purchase good quality rubber boots, rain gear with tops and bottoms, you will need both, and a good all weather hat preferably with a fairly large brim all of the way around.
If you have stalls to clean, you will need a good sturdy wheel barrel. The heavy plastic ones will not rust. This is going to be your best buddy, as well as a good pitch fork, a good rake, and an industrial broom. The kind of pitch fork you will need depends on the type of bedding you choose to use. Next, you will need good brushes. You will first need a grooming box. These are fairly inexpensive. You need a good curry comb, a hard brush and a soft brush. Also a comb or brush for the forelock, mane and tail. There are several good sprays for detangling tails that make the job of combing out a horses tail much easier, as well as helping you in not pulling out too many hairs in your horses tail as they need as much and as long of a tail as possible for swatting flies and gnats. Buy a good hoof pick and not just one. Hoof picks disappear faster than any other horse equipment you will possess. You will need some good rub rags. These are used in a circular motion on your horses coat after you are done using the curry comb and brushes. It will really make them shine. The next thing in line is having good shanks (long rope or leather leads that attach to the halter). When you are turning your horse out or bringing them in, always snap the shank onto your horses halter as they are walking. This aids in the prevention of a loose horse. You will need to tie your horse up in the stall or in the isle of the barn for grooming. I suggest if you are going to groom your horse in the stall, put in a screw eye or some other form of hardware that can be screwed into the wall of the stall in a very secure manner. Make sure it has some type of metal ring for attaching either a tie chain or running the shank through it. The screw eye would be placed in the center of the wall about six or eight inches above your head. If you will be grooming your horse in the isle way, then you would use cross ties. These are long enough rope like shanks, with snaps on the end of each that will snap on both sides of the horses halter as he or she stands in the middle of the isle way.
Storing your feed is important. Rodents will certainly take advantage of easy access to your scrumptious grain. The best way to store your feed is to deposit it into large drums with tight fitting lids or large plastic trash cans with lids. Keep your hay on palates up off of the ground as hay will become moldy very quickly if it gets water on it or is rained on. If your hay is stored where rain can get to it, you may need to buy a tarp to cover your investment. You also do not want to put it out in the sun as it will most likely dry out causing it to lose nutrients, and may not be as palatable. Consider where you keep the manure pile and how you are going to dispose of it. It must be kept in a separate area because of the flies and gnats, and particularly away from any grazing horses as this is an infestation area for parasites. Unfortunately your manure pile will give off an odor and you want to try and keep it as far away as possible but at the same time remember that too far away will make your job of cleaning stalls a longer one, depending on how many trips to the pile you need to make each day.
The barn area as well as your horses should be cleaned on a daily basis. You should also have some type of harrow or homemade drag to put either behind a tractor or behind a truck and drag the fields. This will spread out the manure clumps which will prevent grass from growing underneath of them, help the manure to dry up and be soaked into the soil and perhaps keep down some of the parasite population. These are just a few things necessary for your start in the new world of horses, but these efforts are well worth the rewards.