To design a GUI that effectively visualizes complex data, follow these steps:

1. Understand the data: Familiarize yourself with the data, its structure, and its significance.

2. Define the goals: Determine what insights or actions the user should gain from the visualization.

3. Choose appropriate visualizations: Select suitable charts, graphs, or other visualizations that effectively communicate the data.

4. Simplify and filter: Simplify the data and filter out unnecessary information to avoid overwhelming the user.

5. Use color and typography: Utilize color and typography to draw attention, convey meaning, and create visual hierarchy.

6. Interactivity: Incorporate interactive elements, such as hover effects, drill-down capabilities, and animations, to facilitate exploration.

7. Labeling and annotation: Provide clear labels, annotations, and tooltips to explain the data and visualizations.

8. Consistency: Establish a consistent design language throughout the GUI.

9. User testing: Conduct user testing to validate the effectiveness of the visualization and gather feedback.

10. Iteration: Refine and iterate on the design based on user feedback and testing results.

Additionally, consider the following best practices:

- Avoid 3D visualizations unless necessary

- Use intuitive and familiar visualization types

- Provide context and explanations

- Enable user customization and personalization

- Ensure responsiveness and accessibility

- Use storytelling techniques to convey insights

By following these steps and best practices, you can design a GUI that effectively visualizes complex data and empowers users to gain valuable insights.