Five numbers tell an SME owner most of what they need to know: sales, conversion rate, average order value, repeat rate and cost per new customer. Read weekly, together they explain not just what happened but why.
Each number answers a different question. Sales tells you the size of the outcome. Conversion tells you whether the store persuades. Average order value tells you whether customers buy enough. Repeat rate tells you whether they come back. Acquisition cost tells you what growth is costing you.
Put the five in one place, look at them on the same day each week, and act on one of them at a time. The habit matters more than the dashboard.