You picked an excellent beginner project. And, you have a website that makes following her directions very easy.
If you made the straight/railfence blocks from one color way - - or even a different color way on each of those railfence angles, and then used "scrappy" for the nine patches, you would be able to use your stash and have a very nice quilt.
I have done many quilts from Claudia's QUilt Shoppe, including buying her book because I have found her simple, straightforward directions to create a fine quilt that looks as though I had done something far more intricate.
THe best way I know to get "experience" is to DO IT. And, this quilt will help you feel very capable and learn alot about making a quilt.
Go for it - - and use what you have on hand.