These tutorials are a good place to start learning Cube.js.
Cube.js, the Open Source Dashboard Framework: Ultimate Guide - It is "Cube.js 101" style tutorial, which walks through the building a simple dashboard with React on the frontend.
Building MongoDB Dashboard using Node.js - It is a great place to start if you are planning to use Cube.js with MongoDB. It covers the MongoDB Connector for BI and how connect it to Cube.js.
Node Express Analytics Dashboard with Cube.js - This tutorials shows how Cube.js could be embedded into an existing Express.js application.
Pre-Aggregations Tutorial - Pre-Aggregations is one of the most powerful Cube.js features. By using it you can significantly speed up performance of your dashboards and reports. This tutorial is a good first step to master pre-aggregations.
Building an Open Source Mixpanel Alternative - It's a series of tutorials on building a production ready application with Cube.js.
React Query Builder with Cube.js - It shows how to build a dynamic query builder with Cube.js React Component.