I'm quite fond of my Luna beads. You can adjust the weight of them to fit your needs and graduate up, similar to how Ami comes with three different sets. Just instead of three whole sets it's customizable.
What would be a good vaginal exerciser for a beginner who has given birth?
I would think that any brand is just as good. If you might need a smart ball that is slightly larger to work with, the Fun Factory smart balls are slightly bigger than the Je Joue Ami.