Someone asked something similar here, but no one answered, so I will try it.
I've just done a clean reinstall of my system, in which I have a 1TB HDD + 8GB SSD, which was used before for Windows' Fast Boot or something. I formatted it and installed Ubuntu GNOME 17.04 in it, and it works like a charm. Currently I have 1.5 GB of free space in the SSD, and I would like to have more, just in case.
Currently, my somewhat limited Linux knowledge makes me think a good solution for that would be to copy /usr or /usr/share to another partition and create a symbolic link to it at /(root). That's what I've been doing for a few years now with some folders at my home directory, like the Dropbox folder.
Can I do that? If not, why, and what would be a better alternative?