Let the client direct you as to what is most meaningful for them. Typically in moments of high activity or spend, clients want reports weekly, so they can keep a finger on the pulse. Other than that, month to month makes the most sense. This should also align with your billing in a way, as the report, helps show them what they’ve received for the additional investment.
Quarterly reports, or annual, should also be used as opportunities to revisit the strategy, business objectives, and to bring more macro learnings and opportunities to the table.