Eco Earth works well for the eggs to be layed and developed in. I used a butter tub and filled it about 1/4 of the way with moist, not wet, Eco Earth slighty compessed and placed 4 large female crickets in for a week then I removed the females. I maintained good moisture in the substrate itself and warm temps, around 80F, for about a month then I started seeing teeny tiny baby crickets just a little bigger then a grain of sand. That's when I stopped missting all of the substrate and started misting one spot that had the least crickets around to prevent drowning. Multiple babies can drown in one drop of water. They take quite a while to grow into large feeders, but are great as babies if you have lots of 1st or 2nd instar slings to feed. Then they just progress to feed all sizes of pets. Grain mites are a common issue if you use female crickets from your LPS, but aren't really an issue to the development of the baby crix IMO. The grain mites can also infest your t tanks, where they again aren't really an issue, but unsightly. Mold can be an issue if you keep it too moist, but can be picked off the substrate. You'll need an escape proof lid, just use a thumbtack to make your air holes and make a lot of them. Air circulation is kinda critical, popping the lid on and off a couple times a day should suffice along with your airholes. To feed babies, fill shallow bottle cap 1/3 full of ground up dog or cat food and nussle half way into the substrate away from the area you mist to prevent mold on their food. Break a couple tooth picks in half and lean against the inside of the food dish to act as a ramp for the babies to exit the food dish. You'll need multiple containers set up the same way to sort the sizes of your crickets, because the bigger crickets will eat the babies even if there is abundunt food available. They do start to really stink as they get older, but strong odor in the babies container is a sign of poor air circulation, the babies should be relatively odorless. Sorry for the long response, this way has worked really well for me, hope this helps you some.
Mating the crickets is actually unecessary. If you buy say a dozen large crickets chances are you'll have several females ready to lay eggs. Females have what looks like a "stinger" on them which is their ovipositor (egg layer). Since the crickets were most likely kept in a colony nearly all the sexually mature females will already be pregnant, so mating is unecessary unless your interested in the actual mating process. When you place you few females in the container they'll take a couple minutes to get settled in, but will almost immeadiatly start laying eggs. You'll see the female stick her ovipositor in the substrate and lay an egg. The egg won't be visible, because of being buried and so tiny, but will develop and become bigger and resemble a mini grain of rice. She'll keep doing this in her spair time, which she'll have plenty of. No males will be needed in your container, just a few females for about a week (depending on how many babies you want). 5-6 females for a week will result in hundreds of babies. You must be patient when waiting on the eggs to develop, it could take some time maybe a month or longer. The warmer the temps the quicker the eggs develop, 75-80F is perfect. Since it's getting colder it could take slightly longer. Always smell the babies container and be sure no strong unpleasent odors develop, if odor does develop, increase air circulation and mist slightly less.
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