Certainly, your approach of considering CPC and ACOS to set a stop 10-20% below the last 30-day average CPC is a solid foundation. To enhance this strategy:

  1. Extend the Data Window:

    • Expand your average calculation from a 30-day window to 60 days. This provides a more comprehensive dataset for setting minimum bids.
  2. Flexibility for Inconsistent Keywords:

    • For keywords with lower conversions or higher ACOS, consider adjusting the minimum bid by more than 20%. This accommodates the variability in performance.
  3. Align Maximum Bid with CPC:

    • If you don't have Target Out of Search (TOS) placement adjustments, bring your maximum bid closer to your CPC. This ensures a balanced bidding strategy.
  4. Consideration for TOS Placement Adjustments:

    • If TOS placement adjustments are in play, be mindful that your CPC may be higher than your bid. Adjust your strategy accordingly.

By incorporating these considerations into your approach, you can develop a robust strategy for determining minimum bids with bid automation, catering to the diverse landscape of keywords in your advertising campaigns.