My method is slightly different, and would essentially cost more to set up but operates pretty efficiently, especially when you have quite a few dragons. I employ 4- 55 gallon aquariums I’ve acquired over the years. I basically turn over each tank fresh every 4-5 months, or about the time it takes for them to become adults. By spacing each fresh start about 5-6 weeks apart, I have a constant supply of small, medium and adult crickets. Naturally as they grow bigger and demand more space, they have already been thinned out as I feed the smaller ones to babies and juveniles and save the big ones for adults.
Again, the way used by the narrator works perfectly for smaller scale and will offer you a constant supply of crickets in which you can hand pick out the necessary size you want. I simply prefer knowing that I can open a lid (I use the tape trick and a simple screened flip lid) and every cricket in there should be about the same size.
I start these colonies by taking about 50 (what I assume are about 30 female and 20 male) adult crickets and make sure I maintain a temperature of at least 85 degrees, though I personally prefer 90+/- a couple. The heat increases the likelihood of them mating and within 1-2 weeks they will have already begun laying eggs. These Eggs hatch quickly and within a month those 50 crickets could be hundreds if not more. Be sure to feed them, I use the same mix of dried cat and dog food ground really fine as well as some greens usually left over from my beardies.
How ever you choose to set up your cricket colony, there is plenty of great information in this video. Check it out.