Zumba is a registered trademark so any instructor offering live Zumba classes should be following the Zumba training and therefore the foundation steps should be consistent across classes.
It is best to start with one of the Zumba programs that includes a few different workouts. Try Amazon or Ebay. These tend to have a basic introductory class included where you can learn the steps as well as longer dance workouts where you can sometimes select a learning option that breaks down some of the harder steps. Some of them come with toning sticks and other accessories.
I started with the Zumba Fitness Total Body Transformation System which included toning sticks, then tried Zumba Exhilirate Body Shaping System and then Zumba Incredible Results which uses a small step platform. I didn't get the proper Zumba Riser step, instead I use the platform from my high step which works well.
I also managed to pick up some Zumba ZIn instructor training DVDs that have dance choreography for different songs that instructors can learn and then teach to their classes. These all have the same basic steps that I learnt in the programs as the foundation.
One thing to point out, if you are doing Zumba on carpet you may want to invest in some carpet gliders that fit over your shoes. This allows you to do pivot moves, twists, etc without your feet sticking and possibly resulting in a knee injury.
Hope this helps. Good luck.
