I personally use cricket quencher by flukers and any leftover veggies I have. You can also feed them the dry bearded dragon food or cricket/dubia diet.
We don't give our dragon crickets. In the beginning we found them to stink to high hell and they died off quickly. We literally threw out more than were eaten. After that, we switched over to dubia roaches and black soldier fly larvae. The roaches get fed pretty much the same thing our dragon does, a varying combination of collard greens, dandelion greens, different colored bell peppers, different colored squash, grated carrots and sweet potato/yams. They also get slices of orange to add some vitamin C. In general, the salad that our dragon doesn't eat gets fed to the roaches at the end of the day. They also have a bowl of roach chow and a bowl of water crystals. The BSFL we buy in smaller quantities since they turn to flies quickly. They don't get fed anything other than the bedding they come with.