There are so many out there XD
Dubias or roaches are some of the easiest to breed depending on the species you get. I have a colony that has been with me for around 3+ years now and 1000+ strong and constantly producing <3 love my roaches. I am also getting several other species that will breed like crazy. Stick insects are good, though I am not sure if your beardie will eat them, and they are slightly more complicated. If you have a self sufficient set up for super worms they are easy. Silkworms can be easy slightly more complicated than most roach species. Isopods, simple, make sure they have a little bit of air flow, and some nice humidity and enough soil and food and they will be fine. Crickets are breedable but annoyingly smelly and more complicated than most people want. Wax worms are rather easy to breed, but you shouldn't do too many because they shouldn't be fed off too often. Butterworms CANNOT be bred unless you live out of the US. I have more but those are simple ones and most of the ones I started out with and still have going now.