Once again I will suggest Eleodes The lovable, long lived darklings. Many species are available from many different people online, Peter (bugs in cyber space) as Eleodes subnitens for pretty cheap and they are a pretty good starterspecies.
The larva are easy to keep. I just use coconut coir as substrate, let it dry out and keep some potato and carrots buried.
The adults will eat fruit, dry foods (like cat food, cuttlebones, oats, hermit crab foods, and the like) and pretty much anything you can give them.
A five gallon tank can house quite a few.
Mites are not an issue unless they get on the fruit, but then you just take out the fruit for a few weeks. I never have any big issues with pest in my tanks, as these are desert species and mites aren't really