I don't think it's just one thing.
I would:
-Define a business plan. A plan is better than no plan
-Plan a marketing strategy. You have to make sure there's demand for your product.
-Make sure it's available on Amazon so there's an easy way to order it.
- Repeat until there's a steady demand
- Continue by executing your business plan
FYI, going retail is expensive and very resource-intensive. You should wait until after you've gone as far as you can go online.