Start with a regular ball, ideally a small basketball. The first couple of sets are more about finding a rhythm and becoming confident in throwing and catching the ball in a stable and reliable way. For the side throws, I usually throw in a relatively flat line, so not upwards, as I primarily want to focus

Start with regular push-ups, then try push-ups on rings. At first, have your rings at roughly waist height to get a feeling. If you feel confident, then lower the rings until your torso is level with the floor when you will later use the ball. Before you move to the ball, try one or two short

Start with less weight than you think you can handle. Aim to work from your core, not from your arms. You should feel your obliques and glutes. However, this is one of these exercises that build the entire core muscles structure, including the entire deep muscle structure, as the core is designed to resist against