Keep ad spend and management separate
Ad spend goes to Google; management covers strategy, setup, optimisation and reporting. Judge both together, as an investment in winning customers.
Start from your maximum cost per lead
If you know what a customer is worth and how many leads turn into sales, you can set the highest cost per lead you can accept. Campaigns are then optimised around that benchmark.
The landing page can bring costs down
A better Quality Score, a clear message and a short form can lower your cost per conversion. Quite often the problem is not the campaign but the page people land on.
Tracking decides what you scale
Without properly measured conversions, budget moves around at random. With GA4 and Tag Manager set up well, you can see which campaigns deserve more budget and which should be paused.