CiviCRM ships with a lot of reports, which is great until you're not sure which ones actually matter day to day. Three we'd suggest keeping on a monthly checklist:

• Contribution summary — a quick read on whether income is tracking where you'd expect it to be
• Membership status — who's about to lapse, so renewals don't sneak up on you
• Donor retention — how many of last year's donors gave again this year, which tells you more about long-term health than any single month's total does

None of these need a data analyst to read. Bookmark them, put a reminder in the diary, and it becomes a five-minute habit rather than a quarterly panic.