A typical Linux installation will need somewhere between 4GB and 8GB of disk space, and you need at least a bit of space for user files, so I generally make my root partitions at least 12GB-16GB.

Is 50gb enough for Ubuntu?

Yes, for most things. A basic installation of Ubuntu with KDE or Gnome installed will come to about 2.5 to 3 GB of disk space usage. Couple that with the fact that most packages available for Ubuntu are relatively small (except for office packages, bigger games, Steam, etc.) then 50 GB will be plenty.

How much space does Ubuntu take up?

According to installation procedure 4.5 GB approximately for Desktop Edition . It varies for Server edition and net-install . Please refer this System Requirements for more info. Note : On a fresh install of Ubuntu 12.04 – 64 bits without any Graphic or Wifi drivers took approximately 3~ GB of File system space.