After 3 tries, I finally passed the Core Exam. For my 3rd try, I did around 15 Beginner and a few Intermediate challenges. The extra practice helped me get through the the practical data questions much quicker, which then gave me extra time to research/solve some of the trickier multiple choice questions.
I am planning to do the Predictive Analytics udacity program next if I can find some time. I just started a new job, so am spending lots of time ramping up there. I'll do what I can with the extra time I have and see how far I can get in 30 days.