I used up 4GB, but only because I made myself use all of my GB for the month. Since I'm paying for it, might as well use it up! But if I didn't torrent on it and etc, with just music streaming and some (very little) youtube watching, and web surfing, play store downloads, 2GB is probably the most I would use.
Since I'm in the country where internet options are limited, I've gone the route where i would buy a 4g hotspot (millenicom) for cheap and I get 20GB of usage for home and mobile. It's a little more costly, but considering I'm using it for both home and mobile, it comes to $35 each. Much better than upgrading through verizon and paying for more and getting less.