I do fruit and, as kr1 mentioned above, hamburger quite a bit. I have a
Nesco FD-75R that I bought based on the recommendation of an author of a book about dehydrating meals for backpacking. She ran two of the constantly for a long time while writing the book. You can add some ridiculous number of trays, 12 total I think, if you are serious about dehydrating a ton at once. The FD-75R is more powerful than a lot of the units that I looked at, plus it has the adjustable thermostat that has been pretty accurate in my usage so far. I have been really happy with the unit and have put several hundred dollars of food through it.
What I usually do is go get a case or two of fruit during my once or twice a week Costco trips specifically for dehydrating. You do not need any preservatives, sugar, or anything else to make great tasting fruit. You might want to dip some fruits in lemon or other acidic juice before dehydrating just to preserve colors and texture, but it's not necessary. The FD-75R came with a booklet that had a really comprehensive list of foods and how to prepare and dehydrate them.
As mentioned, hamburger is a great choice. Thick soups/stews like chili also work really well. I haven't messed with jerky much, since really good stuff is so easy to buy and a heck of a lot cheaper. Fruits without a million preservatives and a pound of sugar are very hard to find outside of Trader Joe's though, so fruits are a good choice. Apples, pineapples, melons, cherries, and pitted fruits (plums, peaches, pluots, apricots, etc.) all work really well. Our favorite are granny smith apples and pluots (hybrid of plums and aprictors). I do not really like the way that bananas turn out, and citrus fruits will not work well in a dehydrator.
Follow the directions in the book of whatever unit you buy, and you'll be fine.