One thing I think we should clarify just to preclude any confusion -- you can use your iPad anywhere without Wi-Fi *or* cellular. All your apps will still function as normal (unless they require Internet access, like say the Google search app).
We've interpreted your saying that you "want to use it anywhere" to mean that you want to have *internet access* at all times, (almost) no matter where you are. For that purpose, you might need cellular data, particularly if you are traveling and using the device for navigation, for example.
As I live in a reasonably big city, I've found that I don't need cellular for my iPad, as I am never very far from a public Wi-Fi hotspot, a coffee shop/library/et al, or our downtown zone which has free Wi-Fi. On the very rare occasion that I'm not near free Wi-Fi, I can use my iPhone to "tether" its cellular data like its own "Wi Fi hotspot" that my iPad can use, but this happens only rarely.