I have a Nesco American Harvest. It makes jerky in 6-8 hours! The most important thing is to make sure the dehydrator you get has a fan or you'll be waiting 12-24 hours.
Just get a roast (or turkey breast), freeze a couple hours to firm it up a bit and slice it THIN (1/4 inch or thinner).
Place thin slices in a bowl. Add enough of a marinade/sauce to cover meat, you can use soy, low sodium soy, worcestershire, or teriyaki sauce (or any lowry's marinade or plain old Italian dressing!). If using marinade or dressing, you don't need to add anything else. If you use a sauce, add a sprinkle of garlic powder (or minced garlic), onion powder and meat tenderizer (Adolph's has no MSG, so I use that.). (Meat tenderizer is salty, so don't overdo it. Meat tenderizer may not be necessary for turkey, though.)
Marinate the meat for 2-8 hours, mixing up with your hands every once in a while to make sure it all gets flavor.
Place slices on dehydrator and let it go! Check after 4 hrs and every hour after, rotate trays and take off any pieces that are done.
Simple! I make 3 lbs a week for my darling husband, it is his favorite snack for working the overnight shift.