Audience overlap happens when you are targeting the same segment of customers in two places, which creates unclear results as to which segment is driving purchases.

4. Setting budgets

Once you have set up your retargeting campaign, complete with multiple audiences for each segment of your funnel, it is time to start monitoring them and optimizing your spend.

Knowing how much to spend each day on each segment of the funnel requires some testing. Begin with setting low or moderate daily budgets for each audience (e.g. around $20 to $60). 

You can decide how much to initially allocate to each segment of your funnel based on the estimated audience size given in Facebook Ads Manager: