I've has reasonably good luck with raising Mealworms. It's pretty straight forward, and I know I'm using rolled oats for their bedding/food, which is probably second best to wheat bran, from all the research I've done. You want to keep the medium dry, between 75 & 79 degrees for optimum turnover. I cut up carrots & sprinkle them on the bedding so the worms can get their moisture and maybe a little nutrient from it. I tried celery & now use it in very small amounts because it adds too much moisture. And lately, after reading a thread on here (I think), that someone had some really good luck at speeding their production by taking the skins from an eaten Kiwi fruit & laying on top of the bedding. Skin side down. I tried it & they really like it. I'm sure lot of experimentation would be in order. Temps are important & when you get in the 'sweet spot' you'll see the activity speed up. There's lots of info on the net with all sorts of videos. It's helpful to have at least 3 different plastic trays for the different stages of growth, which I look over on a daily basis. The beetle tray has been cut out on the bottom & screen put in so the tiny worms & eggs fall through so the beetles don't cannibalize them. I figure if I can do it anybody can. It's really simple & other than the oats & a few carrots, I've only spent about $25 for trays in the year I've been doing it. I like the 28 Qt Sterilite ones from Walmart & the tops are handy. Good luck.
