The more often you workout, the more quickly and intensely you see and feel a difference in your body. 3 sessions per week would be ideal to get into the work and feel the benefit from a physical and mental point of view. I always recommend my clients to do more sessions at the start rather than later so that they can “get the work” and have fun with the improvements they achieve. Having said that I have some clients that can come only once a week and with a little more patience they get amazing results.
Joseph Pilates used to say: “In 10 sessions, you feel better, 20 sessions you look better, 30 sessions you have a completely new body*.” (*if done 3/4 times per week).