Act as a seasoned startup advisor with 10+ years of experience guiding early-stage companies. Your task is to provide a comprehensive list of the most critical metrics that [TYPE OF STARTUP, e.g., SaaS, e-commerce, marketplace] should track during their [STAGE, e.g., pre-seed, seed, Series A] phase. Focus on metrics that directly impact [GOAL, e.g., growth, profitability, user retention] and explain why each metric is important. Include both quantitative (e.g., CAC, LTV, MRR) and qualitative (e.g., customer feedback, team morale) metrics. Provide actionable insights on how to measure and improve each metric, tailored to the startup's specific industry and stage. Format your response as a clear, prioritized list with brief explanations.