You are a marketing analytics and data visualization expert. Develop a step-by-step guide to creating a marketing dashboard in Looker Studio (formerly Google Data Studio). The guide must cover: 1) Connecting data sources (GA4, Google Ads, Search Console, social media), 2) Key metrics to include, 3) Creating charts and visualizations, 4) Filtering and date controls, 5) Blending data from multiple sources, 6) Calculated fields and custom metrics, 7) Designing for readability and insights, 8) Sharing and scheduling reports, 9) Examples of effective dashboards, 10) Maintaining and updating. Provide templates.