"blank slate"
1. Definition:
(n.) undeveloped, free of information or associations; the idea that all knowledge is learned, that you’re born knowing nothing
Examples:
My little brother is new to the world of rock music. He’s a total blank slate, so I intend to show him all the coolest bands and make sure he has good taste.
When you first start your blog, it’s a blank slate. It can be whatever you want it to be. But as you gain readers, they’ll develop expectations.