Before a student start a concept, BuildUp estimates if they are ready to learn this concept yet, based on their other work to date. This "tip" is provided in the name of the buttons against each concept.
In this image, you can see that some buttons are labelled "Keep going!" or "Let's go!", which indicate concepts that the student is ready for.
"Give it a try!" indicates that the concept seems like a stretch for this student, and other concepts may be more suitable first.
"Practice" indicates that the student already has a good mastery of this concept.
These suggestions are closely related to the recommendations that students receive at the end of each lesson.