Measurement plan, tracking and data quality
Before any tool goes in, there is a measurement plan: which actions count, what they are called, and what additional information travels with them. Without that list you end up with events under similar names that nobody can tell apart later.
Depending on the situation we implement it with Google Analytics 4, with low cookie tools such as Plausible, or with a self hosted Matomo instance. The data comes from a data layer in the source code, and for shops from the usual events along the purchase path: product view, add to cart, checkout start and order. For WooCommerce and Shopware we build that into the theme or through a plugin, so cart and order values come from the system rather than being scraped off the page.
Sources that need no consent come on top: server logs, status codes, loading time measurements and Search Console data. The result is a report with a manageable number of metrics, each one tied to a decision it supports. Everything else stays available inside the tool without having to occupy anyone every month.
