Hi there, I buy micro sized worms or eggs and raise them and feed them off when they become appropriate size, I buy 500 at a time- sounds like a lot but I haven't yet got to the stage where I have enough to keep as cocoons, It lasts me about a month but i feed to 7 individuals of varying appetites. I keep mine in 7x5" plastic boxes with worms on a piece of mesh so the frass falls through and makes cleaning easier- I sterilise my hands, forceps , boxes, mesh etc every time I clean them out which is every day, but that's just my method.
Remkon is now raising worms and breeding moths and he's just written lots of info about how he keeps his, with full info about boxes, chow etc. Search 'silkworm care' and you'll find his posts here.