Which parts should you wait and see about, and which parts should you keep in inventory?
I buy a lot more online than ever before, as even the so-called fabric stores are mostly about Home Decor, and not at all about dressmaking, whether doll or human sized.
When I buy fabric, stores like Mood will always offer the option of buying matching thread, and I now take them up on the offer. When Designs by Jude has a notions sale, I take them up on it. When I order from Asian vendors on Etsy, I try to include the notions requirements from several projects.
And sometimes, no matter how carefully you plan, you have to order and wait.