It is supposed to be accurate. Diaper changes - as long as you keep her bottom clean and dry there isn't a need for anything. I don't recommend ever using powders anywhere on her body. I would save creams such as Baalmex or Desitin Daily for the times her bottom gets red. You probably won't need it much.
Wipes nowadays are fairly safe since they took out the alcohol.
Chose a diaper that doesn't irritate her. Some like the new Pamper's. As with powders, there really is no need for baby oil. Same with cradle cap, it just hides it. You really don't need oils or powders.