Not all documentation deserves to be in your first training set. The best launch sources are current, customer-facing, and written in the language your customers already use.
Start with high-confidence sources
Help center articles, billing FAQs, setup guides, and one canonical product handbook usually create the strongest first assistant. They answer common questions without pulling in stale internal assumptions.
Leave noisy content for later
Old release notes, meeting notes, internal experiments, and outdated PDFs can reduce answer quality. Add them only after you have a baseline and a review workflow.