Though I don't own 13 dragons or breed them..been around long enough to know what most do. Most breeders mail order in bulk their crickets then feed them a quality gut load, either something the make themselves or buy in bulk as well.
Some do breed their own insects but I find those who do don't have huge amounts of dragons.
Where it comes down to is time and space. It takes some time and amount of work to raise your own feeders. Even if the feeders are easy to breed (and most are) they still have to be maintained...tubs cleaned, insects feed, care to prevent escapes,etc.
In many cases it is far easier to buy 1000's of crickets every week, dump them into tubs or large garbage cans and rotating them every so often so one can be cleaned out. Then they can be fed, watered and fed to dragons as needed.
Just decide what you want to do, breeding your own feeders does safe a little money but often, the time and effort needed doesn't make it worth while...if you don't' have a place to keep noisy adult crickets, like an outdoor shed...or basement, you may find the chirping of several hundred males rather annoying. And they can be loud indoors. Silkworms, hornworms and superworms, far more silent but have their own care requirements...same with roaches. You also have to ensure you have enough to feed your colony all the time, especially if you are breeding and have different ages to feed. If you have all adults, its not as difficult as you just need one size.
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PHLdyPayne