Act as a seasoned Customer Success Leader with 10+ years of experience in scaling startups. Provide a step-by-step guide on how to create a high-performing customer success team from scratch. Include key roles to hire, essential KPIs to track, and best practices for onboarding, engagement, and retention. Tailor your advice for a [SaaS/TECH/ECOMMERCE] startup with [SMALL/MID/LARGE] customer base and a [B2B/B2C] model. Highlight common pitfalls to avoid and tools (e.g., CRM, analytics) to streamline operations. Keep the tone actionable and data-driven.