The page says my predictions are rough.

There are only a few days of sales so far. Keep logging sales; the insights get better every week.

No sales have a customer attached yet. Pick the customer on the POS before taking payment.

How to use Sales insights.

Sales insights turn your sales history into a to-do list: what to prepare tomorrow, what to order, and who to expect.

Open Reports and choose Sales insights.
In Based on, pick how many weeks of history to use and press Apply.
Read Expected best sellers for the next day so you can have them ready.
Check Best sellers by day to see your average sales for each weekday.
Use Next 7 days and what to order: it shows expected sales per item and a Suggested order that covers a week plus 20% spare, minus what you have In stock.
Look at Top buyers per item and Customers likely to buy again this week to see your regulars.

Ring up every sale at the POS, even quick cash sales. Each week of sales makes the forecast sharper.
Pick the customer at checkout. Only sales with a customer count towards top buyers and regulars.
Turn on stock tracking so In stock shows real numbers instead of Not tracked.

Nothing directly. You can use the regulars list to have their usual item ready or send them a message.

The page says my predictions are rough.: There are only a few days of sales so far. Keep logging sales; the insights get better every week.
Top buyers is empty.: No sales have a customer attached yet. Pick the customer on the POS before taking payment.