Idea: Narrow down broad audiences in order to reach people with the highest purchasing potential with a limited ad budget.
Details: First, ensure your offer is relevant to the audience you're targeting. Instead of targeting a large audience with a single offer, identify an offer that resonates best with a specific audience.
By doing this, your ad relevance score will inevitably increase. As our friends at KlientBoost explain, one of the worst damages of targeting too broad of an audience is that you may not reach the people with the highest purchasing potential due to a limited ad budget, leading to the Iceberg Effect.
Take steps such as excluding people by interests, behaviors, age range and demographics. If you're using custom audiences built from your existing customer base, try narrowing down your audience to the most engaged (think 5 star segment on MailChimp lists) first.