Stay within your budget.
Signing up for AdWords is free, and you’ll only pay when your ads are working.
Only pay for ads that pay off.
AdWords won’t charge you for displaying ads. Instead, you pay only when someone clicks your ad, views your video on YouTube, or calls your business.
As for setting a budget, it’s your call. Some businesses spend tens of thousands of dollars a month, and others are comfortable investing several hundred.