Paola..
I've just recently been hooked on Cathe. I first bought her Classic Aerobics DVD and the the Boot Camp/ME dvd. Then the Blast Series. I've also picked up some of the IMAX and the new circuits. Step in motion accidently sent me the Beg/inter step and body fusion. I'm an inter/advanced workout person and was working out 5-6 days a week until June when I got this nasty cold that hung on. I did the body fusion/step workout as my first workouts after being sick. If you are an advanced stepper, then you might not want this one. However, I'm planning on using it on lower intensity days or days that I don't have a lot of time. The Body Fusion section I would consider "aerobic weight training." Uses lighter weights and keeps the old HR up. (I haven't done the other new ones yet, so can't tell you) I really like the adds on she had (lower body, upper body and stability ball abs) My first day back, I did the Basic Step and stability ball abs. My abs are still sore!
Anyhoo, In my opinion, BC/ME is not too hard to start with either. It was one of the first Cathes I got. Boot Camp is circuit type training.
Also, I believe in saving dollars. Buying the entire series is usually a better bet than one at a time. I bit the bullet and got the entire Body Blast Series (timesaver comes with the series). No regrets. Tough workouts, but aimed at every body part and include cardio. I don't want to blabber on here, but just trying to give you an overview of my experience. If you have any specific questions about the workouts, I'd be happy to answer.
IMAXs are really tough and you aren't supposed to use more than twice a week. Believe, when Cathe says tough, she means it. I was whipped and I'm in pretty good cardio shape. I'm going to have to work back up to them after being sick. Darn it.
What you first start out with would also depend on what you enjoy doing the most....i.e, the step aerobics, the weight training, core training
Am I helping at all? Or just adding to the confusion.