I have this one here.
Amazon.com: Nesco American Harvest FD-1010 Gardenmaster Food Dehydrator: Home & Garden My only one I have ever had, but no real complaints. You can add more or less trays as you need to, and they have plastic coverings for things like roll ups.
Compared to smoking, I like the jerky on the smoker better. The dehydrator was still better then most store bought jerky though.
You want some sort of temperature control. I believe some of the better models come with a fan control too. I think some even have an automatic shut off after so many hours, which is nice if you leave it alone often.