Start with the business decision, then choose the metric. If you are deciding whether a campaign deserves more budget, reach alone gives an incomplete answer. You also need to understand the quality and cost of the actions it produces.
Define a useful conversion. An enquiry, trial or purchase may need qualification before it represents value. Agree those definitions with the people who handle the next step, and check that events are recorded consistently.
Read channel numbers in context. Different platforms can claim the same conversion, so attribution should be treated as a model rather than a complete record of causation. Compare the reports with actual customer and revenue information where possible.
Keep the report small enough to use. Explain the activity, outcomes, uncertainty and recommended next action. The point of measurement is to make a better decision, not to fill a dashboard.