I buy several types and offer them in different bowls to the crix. I feed them Cricket Crack, Bug Burger (dry), wheat bran, bee pollen, rice cereal, spirulina, alfalfa, Flukers High Ca Cricket Diet, Bug Buffet, organic spring salad mixes with assorted fruits, etc... I just make sure they have 3-4 different kinds at a time and rotate.
I think rotating is a good idea. Studies done on commercial cricket diets have shown they often do not actually meet the stated min and max calcium contents. I do remember that the Trex food did test as accurate so that's a good one to use. Flukers was tested twice on different occasions and had much less calcium than advertised both times.
You can make your own gutload too, you just need to use calcium carbonate to obtain 8-9% Ca (by weight) and feed 48 hours before the crickets are used. You can get exact details by looking up studies by Mark Finke.