Please note that I watched MANY videos in preparation for mine and the most common hick up I've seen is the skirt portion of the cake is too short for the doll. In my video I explain the process from beginning to end so you can avoid this.
Day 1 decorate the doll and make your accent flowers
Day 2 bake the cake then wrap and refrigerate (be sure to measure the cake to ensure it is the correct height if not you'll have time to bake more)
Day 3 fill the cake and apply a crumb coat to the cake, if working more than a few days in advance it might be preferred to freeze the cake at this point.
Day 4 on the day before your party you can assemble the whole cake
Now that you have the general idea here are some tools you might want to purchase.
** In the video I used 1 box of chocolate cake mix, it was enough to make a 6" cake pan and a 6" ball cake pan
Chewy candy such as Starburst or Jolly Ranchers