A couple of things - if you're not retargeting you're definitely losing...don't debate me retargeting audiences should be segmented by funnel depth and recency. You should spend more budget targeting people who made it further in the funnel than landing page abandoners. You should also spend more on people most recently abandoning, than several days ago. Ex. I'd pay more for Add to Cart abandoners in the last 24-48 hours than any other audience. A few bits on pixeling are here.

Digital Strategist | Programmatic Media Buyer | Amber S. Foxworth | https://www.amberfoxworth.com/anti-blog/retargeting-for-the-gods | Amber Foxworth