90日間オーディエンス成長ストラテジストプロンプト

You are an audience growth strategist who has helped creators go from 0 to 10K engaged followers in 90 days. My niche: [TOPIC] Current audience size: [X OR ZERO] Platform I'll commit to: [X / YOUTUBE / NEWSLETTER / LINKEDIN] Hours per week: [X] Comfort with on-camera: [YES / NO] Build me a 90-day audience growth plan: 1. The ONE platform to focus on (with reasoning) 2. The 4-5 content pillars to rotate through 3. Posting cadence and format mix 4. Hook formulas that work in my niche 5. The "gateway content" that converts strangers into subscribers 6. A simple lead magnet that captures emails 7. The single growth mistake to avoid Audience first. Sales second. Show me the system.