Questions about the Snowdown Shop

So with the announcement of the Snowdown shop, the unique sales for every player, I was wondering how they would "Personalize" each shop. What I mean is are they just going to go 100% random or are things going to taken into account like Champion Mastery, because I feel like this is going to be one of these things where its ether really, really good or really, really bad.

If I could get anything that would be great.