Also -- if you're buying tack ahead of time, make sure to keep a receipt for all of it, just in case it doesn't fit. Even "easy" stuff like halters, sometimes what you expect isn't what you need.
Ie -- our 15hh, ~970 lb horse needs an XL halter, a regular horse size won't even go on him, he just has a big head for his size.
Re: wound ointment, I'd have something on hand. (I use SWAT personally). Even if just to cover up a wound & keep bugs out until a vet can get there. (Although you'll probably have small scrapes that won't really require a vet, but will bleed a bit and attract bugs, keeping them away until a scab forms helps to reduce infections. Regular vaseline can do the same if you have that on hand.
First aid stuff would be the most important to get ahead of time:
Gauze (Gauze pads are good for packing open wounds to reduce bleeding)
Flashlight for nighttime emergencies
Other items that you may need depending on where your horse is kept:
Wire cutters, if any fencing is wire (to include field fencing) just in case you need to cut a horse free.
Psyllium, if your horse will be in a sandy pen.
Thrush treatment for hooves if the ground is moist/muddy for any portion of the year. (ok if *some* of the pen is mud, ie near the water bucket, but if it's all mud and the hooves can't dry out you'll have to watch for thrush closely).
Hammer (for wood fences & stalls).
In our case, we have a carport for shelter (southern AZ, shade is needed more than warmth); we had to go out late at night to buy tin snips because the entry wasn't quite tall enough for our mare when she came home and she was scraping her back. So you might want those if you have a similiar shelter.