How to Approach with Math here?

Hello KhanAcademy,

First of all i would like to thanks for this great website and effort you are making this engaging for students all around the world. I wish i could support donated some monies, but due to no PayPal and available funding method right now i can't do it. But eventually i will ended up doing it in future.

Anyway what I wanted to know that what would be the best way to learn math from here, should it be goes by grade wise. or should it be done Subject wise. Which would be better.

Thing i would like you to know that i am a step by step learner. So i would prefer to learn step wise, nothing in advance. 

Thanks