I do all the above and More. Simple things like banking the shavings in the morning (horses have 24/7 access to stalls) and pulling down to make a bed at night. Saves on shavings and time mucking. A $1.79 kitchen strainer to skim the water buckets saving on water. Mixing more expensive hay (T and A) with less expensive grass hay because its gotten so expensive and my horses don't work that hard. Buying vitamins and supplements in larger sizes (I have 2 horses and a pony) and not so great pasture. Learning to trim feet (mine are barefoot). Give my own shots when possible. Like Hippolyta, I buy what I can at the dollar store (hair brushes, combs, cotton, alcohol, etc..
I also make a lot of equipment. Saddle pads, browbands (50 cent belts at the Goodwill, a couple of Chicago screws and TA DA.....custom browband). I've even made half chaps from an old pair of suede boots.
"I've spent most of my life riding horses. The rest I've just wasted". - Anonymous
Mulch is great for trees. A tree surrounded by grass is starving. Trees in a forest are surrounded by natural mulch.
Two important points:
1.Keep the mulch 12 inches away from the base of the tree.
2.Don't smother the tree with mulch, spread it 3-4 inches thick max. As large as an area you desire. I reduced my mowing greaty.