1. Conversions against the store
Before anything else. If Google says 300 and Shopify says 190, every other number on the screen is decoration.
2. Search terms sorted by cost
Twenty minutes here finds the wasted spend in almost every neglected account.
3. Brand share of spend
How much of the "performance" is people who typed your name. Usually more than the last agency admitted.
4. Merchant Center diagnostics
Disapprovals nobody checked, often double-digit percentages of a catalogue.
5. Change history
Tells you whether anyone has been running it, and whether they panic.
Then structure, then bidding — last, always. The full sixteen.