It's not easy to learn, especially if you are not strong in math, but if you want an intuitive understanding as to how machine learning works, I would recommend learning a combination of probability, linear algebra, and formal theories of computation (abstract machines):
This book was really what opened the gate of tying the content together:
http://www.amazon.com/First-Course-Probability-9th-Edition/d...
You should also be strong in discrete mathematics.
A First Course in Probability: http://www.amazon.com/First-Course-Probability-9th/dp/032179...
Linear Algebra with Applications:
http://www.amazon.com/Linear-Algebra-Applications-Otto-Brets...
Note that the Bretscher book has really terrible reviews, but I can't evaluate if the reviews are correct or not.