A LOT of apps use location services to phone home. Go into Settings --> Privacy --> Location Services and turn it off for apps you don't think need it. Most of my apps don't really need it but turn it on by default anyway.

Go into Settings --> Privacy and click on each app listed. This will show you a list of apps that have requested access to that app. This often means that these other apps are mining data and phoning it back home. Turn off access to apps you don't want accessing each of the apps in this list. BTW, you might be appalled at which apps want to access your Contacts, Calendars, Reminders, etc. Best to curb this snooping by other apps!

Also go into Settings --> Privacy --> Advertising and turn on Limit Ad Tracking. Just like Facebook, a lot of the apps are little more than data mining wastes of time.

These three things will help cut back on apps calling home and thus burning up internet allotments. I'm sure there are plenty of other helpful hints if you search for them.

ETA: You might also go into Settings --> iCloud and Settings --> Mail, Contacts, Calendars to tweak settings for how often and how much is synced and pushed to and from your iPad. Setting these controls could reduce internet usage as well.