Act as a cybersecurity consultant with 10+ years of experience in handling data breaches for startups. Provide a step-by-step guide on how [STARTUP_NAME] should respond to a data breach involving [TYPE_OF_DATA_COMPROMISED] (e.g., customer PII, payment details). Include immediate actions (e.g., isolating systems, notifying authorities), communication strategies for [STAKEHOLDERS] (e.g., customers, investors, employees), and long-term measures (e.g., security audits, employee training). Tailor the response for a [INDUSTRY] startup with [COMPANY_SIZE] employees, emphasizing compliance with [RELEVANT_REGULATIONS] like GDPR or CCPA. Highlight common pitfalls to avoid and best practices for rebuilding trust.