Apple cider vinegar sprayed on the hoof helps get rid of and prevent thrush. It also helps strengthen and condition manes and tails. Buying bulk in everything (buying with other horse friends) saves a lot of money.
Feed more hay and less grain. Toothpaste works well to shine tack metal and can be used on a bit as well! If your bit gets stained with some nasty stuff, soak it in apple cider vinegar for 15 minutes or so and then wash it thoroughly with soap.
Baby powder is good for whitening white markings for shows and baby oil for around the nose and eyes. Dollar store, target, etc are great for many things. You can get cheap antibacterial stuff for treating horse wounds at target. That stuff is the same for people as horses. 1/4 mouthwash, 1/4 baby oil, and the rest water is handy for spraying the top of horses itchy tails (if it is just dry).
Small mesh hay nets are great for gaining weight on horses and loosing weight on them. A little strange but true!
And check out Tack of the Day
They have great sale items!