Tony Spiro's tutorial guides readers through building a fast and simple blog using React, Gatsby, and Cosmic, with an emphasis on integrating the Cosmic source plugin to connect data from Cosmic to a Gatsby site. The process begins with setting up the development environment by installing Node.js, npm, and Gatsby, followed by creating a new site and configuring it with the Cosmic plugin to fetch data using GraphQL. The tutorial includes steps for displaying posts on the homepage and creating individual post layouts, leveraging Gatsby's createPages API for URL management. The project is designed to be easily deployable on platforms like Netlify and offers a foundation for exploring further capabilities of both Gatsby and Cosmic. The source code is available on GitHub, allowing users to clone the repository, view a live demo, and build upon the initial setup for enhanced website performance.