The average person uses at most 10 to 20 GB of data per month.
However some larger users who stream a lot of video or movies or upload or download big files constantly may use 200 GB to 500 GB of data but that is rare.
I'm not sure exactly how much data I use per month but it's likely way under 100 GB of data and more like 20 GB of data.
20 GB of data is usually more than enough data for some people but other people may go through 20 GB of data sooner than other people.