From my experience I didn't start out with the training kits, I got chucked in at the deep end in sort of a sink or swim environment as it was a very fast paced company.

For me nothing beats experience, I have seen many people turn up for interviews who have the certifications, but couldnt actually do the job as you could tell they have just memorised the things required to pass the exams.

While I'm not saying don't use the books as they may be beneficial to you, it's just not the way that I learned.

I used the training kit for 70-432 and found myelf skipping big chucks of it as it was to basic for what I knew.