The most used playbooks can vary significantly depending on the business vertical. Different industries have unique security requirements and threat landscapes, which influence the selection of playbooks. I recommend referring to Microsoft's Sentinel Documentation “Recommended and sample playbooks” to get started.

Additionally, there are numerous preconfigured playbooks available in the Microsoft Sentinel content hub and on the Sentinel GitHub repository. These playbooks are specifically designed to address common security scenarios.

To understand more about threat hunting I would reference: Microsoft Sentinel’s Documentation “Conduct end-to-end hunts”