I completed and passed the exam, my tips are:

• Start with this: Marketo Certified Expert Preparation Tools
• Read through all the Marketo docs - Product Docs - Marketo Docs - Product Docs​ (even know some of the stuff can be simple, I suggest read it all, you will find some hidden features when you read the docs which can then appear in the exam)
• Enroll in Marketo Certified Expert Preparation Learning Path in the University and complete all tasks. I find some University courses can be out of date (i.e. use the old pre 2014 UI), so I wouldn't spend most of my time here but if you have time outside of the Marketo Certified Expert Preparation Learning Path then complete other course too

I found the answers I got wrong in the exam, was on the features that I don't use, i.e. Calendar, that's why the Product Docs is so important as it shows you things that you might not use day to day but may appear on the exam. From what I remember the practice exam is close to the actual exam but I wouldn't personally compare it.

When in the exam, they give you an opportunity to mark a question for review and come back later, this was really helpful as when I came back and read it for a second time, I changed my answer.

Happy studying!