I am by no means an expert or authority on the data usage that the drive app is producing, but I do have a fair amount of experience configuring tablets for drivers and observing their data usage.

If the usage of the Drive app is minimal, or the driver will simply be doing a DVIR and not much else; you can expect under 500MB.

If the driver is constantly working full time / a full rule-set of work time, 1GB - 2GB may be expected.

If there are add-ins, DVIR pictures, navigation, you may see as much as 3.5 GB.

Regards