Some essentials: Google Analytics for traffic data, Hotjar for behavior insights, and a solid A/B testing tool like Fibr. HubSpot and Clearbit help with lead tracking and segmentation. Fibr, again, will help you run free CRO audits and create AI-powered variations of your landing pages. It also comes equipped with CRO agents that automate and simplify site optimization at scale. The best stack depends on what you ultimately want, but every tool should give you more clarity on how to convert smarter.