Mostly partitioning will depend upon what you like to do with your system. However I am attempting to answer assuming typical use.
/home as a separate partition will help you to retain all personal data even when you do a wipe out re-install of OS with same version or higher version. (Such re-install is recommended than upgrade). If you want further granular control you can create more partitions based on need.
Generally you will not have more than 2-4 GB of data (it can vary based on what you install, but if you use default logrotate to keep logs cleared and do not use system for ever growing data like databases) in root if you are keeping only two partitions namely
This assumes all your personal files goes to
/home. So probably keeping ~6 GB to root , at-least same size as of RAM as swap (only if you expect any possibility of 100% memory usage) and rest of space for
/home will be ideal. Also note that all personal files goes to
/home by default,
/home likely to grow over time.