Understand the difference between horizontal and vertical scaling.
"If you've found a campaign that's working there are two ways to scale -- horizontally or vertically.
Horizontally, meaning expanding the target group -- and the budget relative to the size of the target group -- via lookalike audiences, expanded detailed targeting, etc.
Vertically, meaning pumping more budget into the campaign. The more budget, the better the results -- because you're more likely to win auctions and get that valuable impression, click or other desired KPI." -- Christina Albe, Haus von Albe