The amount of jets you need depends on their placement and the appropriate pressure. You should focus more on a lower amount of jets with good pressure that can evenly spread the water. Aim for a maximum of 30 jets per massage pump.  More important than the number of jets is the size and placement of the jets; they should follow the contours of your body, with larger jets for larger body areas, like your back and shoulders, and smaller ones for smaller areas like your wrists and neck.