I agree with Razbo. I'm an intermediate player and I started at the beginning of the core lessons. Even though I breezed through the first parts of it, I picked up some things here and there that were very useful. It was time well spent.

You'll eventually hit a place where it becomes challenging...and then you dig in and go from there.

At the same time, find some songs that interest you that are at your level or jsut above to work on.

Have fun!