i will not promote: How should a solo founder choose a validation wedge?

I’m working on a startup related to China business operations. The initial idea spans sourcing, product development, factory inspections, and production setup. I started with a tea-related use case to test whether a narrow entry point could lead to a broader service. I’ve already spent substantial time building the catalog and workflow: roughly 900 teas and 3,500 tea cakes are documented. But I haven’t yet proved which customer problem should come first. As a solo founder, I’m deciding what to do over the next 90 days: validate repeat paid demand for the narrow tea use case; test one specific China-related service with businesses; or recruit service providers before building more software. For founders who have dealt with a broad marketplace or services idea, what evidence helped you narrow the scope? Did you prioritize paid demand, repeat usage, or partner commitments?