The documentation is organized to help you get started with Gaea quickly and easily regardless of your skill level.
Installing Gaea contains instructions on installing Gaea.
Gaea champions the idea of having multiple workflows to suit the artist and the terrain. You choose how you want to work. You can even change your workflow in the middle of the project without adverse effects. The Workflows section explains the main workflows in Gaea: Layers Workflow, Graph Workflow, Sculpt Workflow
Refer to the Node Reference to learn about individual nodes, their functions, and usage advice.