Look at the frequency. If it’s under 1.2, then you know you have plenty of room before burning out meaning that you have a small budget relative to the audience size.
But don’t enlarge your audience just because you are seeking a low CPE (cost per engagement). Make sure you’re getting quality, too.
Do this by running remarketing audiences against people who have engaged with this ad. And now you are testing a sequence- one of many you can chain together to build a smart funnel.
Don’t get hung up on any one piece of content or one ad. See the bigger picture by having balancing metrics- usually quality vs quantity.