"Start with €50 a day" is advice that fits nobody in particular. The real constraint is conversion volume: automated bidding needs a steady flow of sales to learn from, and that depends entirely on your price, your CPCs and your conversion rate.
Work it out backwards
- Find your break-even CPA. Gross profit per order is the ceiling. Calculator.
- Estimate clicks per sale. If your store converts at 2%, that is 50 clicks per order.
- Multiply by CPC. 50 clicks at €0.60 is €30 to buy one order — fine if your break-even CPA is €40, fatal if it is €15.
- Multiply by the conversions you need to learn from. A steady flow, not one or two a week.
That gives a monthly figure grounded in your business rather than someone else's.
What happens if you start too small
Not nothing — but the account stays in a state where the bidding never has enough to work with, every week looks different, and it is genuinely hard to tell whether the product works or the budget was simply too thin to find out.
What happens if you start too big
You buy an expensive education quickly. Scaling budget into an account with unverified tracking and an unfixed feed is the most common way stores lose serious money on Google.
The right starting budget is the smallest one that produces enough conversions to read. Anything below that is not a test, it is a guess with a receipt.