Hello, and welcome to the HCA!
If you eat a well-rounded diet, whether it be strictly this or that, it makes it much easier to make a routine of feeding your crabs, they need fresh fruits, vegetables, proteins, and a good source of calcium as well. I eat a lot of fruits and vegetables, at least one of each per day, and my crabs most likely are going to get the same thing I did, provided that it passed the safe food list.
I also suggest odd foods for the crabs such as sea vegetables, examples are nori, seaweed, and kelp kombu.
Meats are very important, they are a big source of protein that your crabs will enjoy, they don't need to be cooked, my crabs far prefer raw foods than cooked. I only cook foods that they couldn't eat otherwise. You can try the basic meats like chicken, turkey, pork and beef, but you can also be adventurous and try meats like octopus, squid, crab, and rabbit. My crabs love stinky sea meats, tuna being a really smelly one.
Commercially dried foods are not good choices unless they don't contain any calcium sulfate, this is quite harmful to your crabs in a longterm usage. You can, however, buy prepacked fruits or vegetables that have been dehydrated or freeze-dried, just check the ingredients for any added seasonings. I dry food that I am going to use later at home with my food dehydrator.
I wish you good luck, we are here for you!