This app has in-app purchases for tools. It is Fifty-Three's business model. The app with all the in-app purchases is still under $9 and the quality is excellent. I have used this app as an artist and educator. I have used it with students. It is very intuitive to use. You can create your own journals. This app makes your most basic notetaking and idea sketches look good.
My recommendation is to buy the Essentials package for $6.99 and the Mixer for $1.99 and you will have all the tools.