In the early phase of training, most people focus on raising the bond of their supports. These can be seen in the top right when you select a training. Once every card is bonded, you wait for rainbows, and train Wit or do races if there’s no rainbow, leading to this flowchart:
As you get more experienced you’ll learn what risks you’re willing to take, when to do rainbows instead of bonding, when to raise mood, and so on.