1st is previous buyers/leads/email list (YOUR BEST AUDIENCE) 2nd is website visitors (thank you page, checkout page, etc) 3rd is videos watched 75% or more. 4th is Facebook Engagement (folks that have engaged with page posts or your ads) For large countries example USA, 1% works best. For other top tier countries UK AUS NZ CAN, 2% is better because it gives a bigger audience than 1%. Facebook optimizes better with a larger audience