The direct answer
If people are already searching for what you sell, start with Google Ads. You're capturing existing demand. If your product needs to be discovered or demand created, start with Meta. You're interrupting attention, not capturing an existing search query. Most mature accounts eventually run both, but the starting channel should match the buying behavior of your category.
Search intent vs interruption
Google Ads works by matching to an existing query, so it performs best for categories with established search demand. Meta works by interrupting a feed, so it performs best when the creative itself can generate interest a search query never would.
When to run both
Once a brand has meaningful top-of-funnel Meta activity generating awareness, retargeting and branded search on Google often become disproportionately efficient, the two channels start reinforcing rather than competing for the same budget.
