The biggest money saver I've found is ordering online from wholesale stores, rather than a local farm and barn. Also, I bought my water tank used, and built my own lean to, instead of paying for one pre-made or buying new.
To draw out and abscess, I use a feminine napkin, soaked in iodine salt water solution, and then sprinkled in iodine salt. Stick it to the bottom of the foot, wrap in vet wrap and then cover in duct tape. Stays on pretty good, and really only needs to be changed once a day. Its very inexpensive.
I use bag balm/udder balm as a fly repellant for their ears and tummies. A thin layer keeps the flies off and it is cheap. I also use it to cover small wounds, such as scrapes and cuts, after applying an antiseptic.
Also, to save money, I will try almost any generic horse thing (such as shine spray, fly spray, wormer, etc) to save some money. Some actually work better than brand name, and I'll try almost anything once.
I also use regular cheap human brushes (from the dollar store or similar) on their manes and tails. They work just the same but are cheaper.
I schedule vet/farrier visits with the other horse owner on the property, this saves us time and money on farm visit charges.
I've heard of people giving their own shots, but personally I like having the vet do it. I also know of people that trim their own horse's feet, but they know what they are doing, unlike me.
To keep the water clean in our tank, we put a melaleuca product called Sol-U-Mel in when we fill the tank. It's all natural, you need only a cap full for a good size tank (I have a 100 gallon or so tank), and it keeps the bugs/algae out of it.
Oh and my last money saver, I don't buy gimmicks, such as carrot sticks. They are WAY overpriced. You can use a dressage whip with the end either tied or cut off and it's the same thing as a carrot stick... so I use what I got and that's good enough. The only exception was my rope halter, but I did not buy it through a trainer. I paid 8 dollars online for the same style halter that he wanted 60 bucks for.