Hello! Well, I am also pretty new to all this, but I have done a fair amount of research. From what I understand soilless media is just an inert material and requires a regular nutrient regimine in order to keep your plants healthy and happy. As opposed to soil, which has a certain amount of nutrients in the mix to keep the plants fed for at least the first 3-4 weeks before requiring any kind of additional feeding once the nutrients that were originally in the soil are all used up. A soilless medium is a type of hydroponic growing teqnuique, and needs to be treated as such.
as far as I know, any hydroponic nutrients will work for expanded clay, coco fiber, pearlite, etc. grow. Why not just order a good simple nutrient on amazon? Im using Dyna-Gro, its cheap, effective, and very very easy to use. There are many others, but this is just what Im currently using.
As far as the worm castings are concerned, I would have to let somebody else advise you on this. I would imagine that you would need to use some other additives in order to get a more complete feeding. I doubt these have everything the plant needs to survive in a soilless media set-up, but again, Im not sure on this. You will probably start running into some deficiencies down the road which would be problematic. You could also just go down to your local hardware store, walmart, garden store, or whatever you have access to that has a gardening section and use a fish fertilizer or even miricle grow people have has success with and would be better than nothing... But maybe better for a soil grow. You most likely need something more taylor made for hydroponic use.