A campaign's budget is what you authorise to be spent per day on average on showing your ad. It is the only figure that controls how much you can lose, so it deserves respect from day one.

It is an average, not a daily cap. Meta spreads spend over weeks, Sunday to Saturday: a day with good opportunities may spend up to 75% more (with 10 € a day, up to 17.50 €), and another day will spend less. What it never does is go over 7 times your daily budget in the week. If the campaign starts mid-week, that week's limit is prorated: starting on a Thursday, 3 days.

Start small. The first days are a test, not a campaign: you are finding out whether the ad and the audience work together. A small daily amount, enough for data to build up over a week but not painful to lose, is the sensible start. What counts as "small" depends on your business and on what a customer leaves you.

To raise it, two conditions. You only raise the budget of something already profitable: the return has been above 1 for days and the cost per customer is within what you can afford. And you raise it little by little, because every budget change makes Meta readjust and brings a few days of odd numbers. Doubling at a stroke is the most common way of breaking a campaign that was doing well.

To cut it, one condition. If getting a customer costs you more than that customer leaves you, the campaign is losing money every hour it stays on. Pausing is reversible and free. There is no reason to wait and see whether it improves on its own.

What Markettai does here. BOOST moves budget from the expensive campaigns to the cheap ones and stops the spending when something runs away. The emergency pause cannot be switched off and works on every paid plan; budget moves are either proposed to you or made on their own depending on your plan (see «What each plan automates»). Separately from this, your plan sets how much you can spend per month before a fee on the excess applies (see «The fee when you spend heavily on ads»).