You could specialize or brand-ize.
Focusing on waist cinchers would limit the size range of busks you need on hand.
Single layer corsets require less fabric.
Who is your target audience?
Goths: black coutil and silvertone findings
Steampunks: brown (leather) and brass findings
Fashion Fabrics?
I generally do OOAK custom work - hands on. I pick up random yards of fashion fabrics and add them to my "kit" of options for customers to feel and choose from. I generally have between 20 and 35 at any given time.
If you are offering fabric choices online keep it as simple as you can afford. If you offer red satin coutil for example, be prepared to see a rise in orders for red items near x-mas and valentine's.
How many pieces do you expect to make in 2 months?
Consider your most popular items. Try to keep this amount of stock around at a minimum. You never know when you'll have a supply chain issue (or get a package of supplies stolen or lost in the mail).
I have plans on expanding, but for now, I'm working on a really small scale (2-4 a month). I keep the supplies I need for the
few styles I push. When I only have enough supplies to make 6 of anything - it's time to reorder. I gladly accommodate customers' interest in other styles, with the caveat that it will take time to order parts I don't have. I can always make a mockup with a solid front or a strong zipper while I'm waiting for an emerald studded busk to arrive.
You could always go the ready -to-wear route, separating the customer from all supply chain issues entirely.
Hope this helps!