Practice does make perfect but everyone learns in different ways. For example, I am a visual person, I can watch a video once and learn that workflow or feature tool. Some people learn by reading handouts and books to get a better in depth understanding. Some people learn from repetition by using a feature over and over to get familiar with. So it's really up to you and your learning methods. If you can learn by just playing with the software and getting familiar with the features tools then that's fine. I would recommend watching the videos that are posted on the help menu of AutoCAD. I posted a link below of the topics you will be asked during the AutoCAD Certification exam. If I remember right if you logged in with your Autodesk account and go to the Autodesk certification website and take a practice test. On top of that, there are a few practice exam handouts you can download also. Ascent is another great resource for practice exam books also.
AutoCAD Exam Topics
ASCENT
AutoCAD Practice Questions
Practice Questions
Practice Questions 2