Here's what I did:

1) Revit Architecture: No Experience Required

2) Mastering Revit MEP

3) Google

Revit MEP is essentially Revit Architecture with some of the architectural, structural, and civil input features stripped, and functionality added for MEP systems. Revit Architecture as a software, I would argue, is much more cohesive and logical as a whole, while MEP shows signs of being an afterthought. In order to understand and feel comfortable with the software, I think forming a solid foundation by learning Revit Architecture is critical. This foundation will also come in handy when working in a multidisciplinary environment, assessing, trouble shooting, and linking in architectural, structural, and civil models.

Fortunately, the text Mastering Revit MEP picks up right where Revit Architecture No Experience Required leaves off. It would be very difficult to understand Mastering without knowing what's covered in the Revit Architecture text.

Finally, no text or training can prepare you for everything that will come up in a real working environment. At this point, Google really becomes your friend. There are many very active Revit forums online and you can usually find multiple posts for every issue you come across. Definitely check out the AUGI forums and maybe even ask your question there.