For some students, training once per week is all your schedule allows. It will take longer to learn, longer to reach test readiness, and much longer to reach black belt. But the journey is yours.
Training twice per week is recommended. The more often you train, the faster you learn and the more you save.
If you can train three times per week, you will learn, build confidence and improve your fitness level faster. You also will test more often and work toward earning a black belt faster.