There are alternatives to traditional bone casing though. If you're using plastic boning it will come with a casing. You can also use grosgrain ribbon (but not satin, it's too thin and the bones break through too easily). You can use a tightly woven twill tape as well, or cut your own from the straight-of-grain of a strong fabric like a twill. The problem with cutting your own is that bias cuts tend to bag and let bones twist, but straight-of-grain doesn't smoothly curve.
Another alternative for waist tapes. Petersham is a bit more flexible up-and-down, so it's a bit more comfortable than twill tape. Be sure to get cotton or mostly cotton.
After your grommets or eyelets, you’ll need a cord or string to lace them together. There are many different things you can use for corset lacing. If your corset is short with few holes you may get away with shoe or boot laces from your local department store. Specialty shoe stores sometimes sell longer laces, so check there too. You can buy numerous different types of corset laces from corsetry supply stores online. You can also buy soutache braid by the yard at your local fabric store. Some other ideas for by-the-yard cords: parachute cord, gross-grain ribbon, satin ribbon, and drapery tie cord. Just find what works for you, your only real limit is that the cord has to fit through your grommets or eyelets and stay tied in a knot. Be sure that whatever you use has tips on the ends so the fabric or material doesn’t fray. You’ll be putting a lot of abuse on these laces every time you put them through a hole, so protect the ends. If your laces are bought by-the-yard there are plenty of methods for making a tip on them. You can buy professional liquid tipping solution or cramp-on metal pieces called aglets. Just be sure that whatever metal piece you get will fit through your holes. You can also get heat-shrink tubing at many corset supply places or in the electric section of a hardware store. You can also use superglue to dip the ends in. Just be sure you don’t stick the laces to your fingers!