My recommendation would be to check out videos of accepted sketchbooks, to get an idea of what calarts is looking for. I've noticed they want a ton of figure drawings, they want to see a wide array of styles, mediums, and subjects. But most importantly they don't want to see a perfect sketchbook; they don't want to see a sketchbook full of your best art. They want a true view of your artistic process, they want to see that you won't sit on the same sketch for an hour to make sure it's perfect, they want to see that you are using your sketchbook as a sketchbook, they want to see your mistakes and the want to see how you fix your mistakes. They don't use your sketchbook to measure your skill as much as they use it to understand how you work as an artist.