Many pet shops carry gut-loading food for crikets. Some are packed with calcium, some are packed with vitamins, it depends on what you buy and what your looking for so be sure to read the labels. You want to feed those supplements to the crikets roughly a day before you feed the crikets to your frogs so the crikets GI system has enough time to absorb the good stuff before theyr consumed by your frogs. (a lot of pet shops sell their crikets already gut-loaded but it sounds like you want to breed your own frog-food source) If going natural is your plan, feed your crikets things like romaine lettuce (iceberg is low in nutrition), apples, oranges, carrots, and sweet potatoes. Personally i recommend you consider chipmunk + pluke's advice and feed your crikets spaghetti lol