This week I took some time out to complete the new Dynamo course by Ian Siegel over at Lynda.com. The course duration is just over 3 hours, it took me longer as I followed along with the videos, but I can say it was a very good course. It does a good job of introducing you to a broad range of nodes available in Dynamo and what you can achieve in wiring them together.
The course focuses on the Dynamo plug-in for Revit. You can still participate with Dynamo studio, but there is chapter at the end that focuses specifically on Revit nodes which you won't have access to.
The course can be found here and I would recommend it if you are starting out with Dynamo.