Do you recommend buying the "HP Prime Graphing Calculator App"?

[Eddie W. Shore]

If you are referring to the HP Connectivity Kit and the HP Virtual Calculator? That should already come with the HP Prime.

If you are asking about the iOS or Android app, I guess it is up to you. I prefer using the hardware instead of apps and there is no way that I know of, of transferring programs from the apps to the computer (yet). Personally I would start with the hardware first.