If your pixel or CAPI has even minimal data, start broad - no interests, no restrictions. Meta’s algorithm performs best when it has room to optimize. Use Advantage+ Audience, and focus your energy on high-converting creatives and a clear, compelling offer.
However, if your account is brand new with zero conversion history, begin with 3–5 interest-based audiences (each ideally in the 1M–10M range). This gives Meta enough structure to start learning efficiently.
Once you've gathered around 50+ conversions, switch to broad targeting to scale. If performance drops, consider layering in behavioral traits like “frequent online shoppers” or move into warm audience retargeting.