How much budget should I allocate to a Facebook campaign?

It’s important to define a minimum budget that allows the platform to deliver your ads on a sustained basis. 

When defining minimum budget requirements and recommendations, Meta considers business sector, budget type, purchase type, bid strategy, optimization, currency, and calendar to avoid underdelivery.

Tip:

Allocate budget based on the optimization event: Some optimization events may require more budget than others depending on how difficult they are to achieve (for example, if you optimize for increased purchases, you may need to allocate more budget than if you optimize for landing page views).

If you don't want to increase your budget, you can try optimizing for an event that may be easier and cheaper to achieve.