I find the simplest way to install Ubuntu with MATE as the desktop with the minimum I can get away with is to start with the server ISO. Yes, I know there are smaller initial downloads when using the netboot image but that means you need to set up the whole net booting server system. That seems to be over kill and involves a lot more downloading and work. Especially when you are only going to use it once.
The resulting Ubuntu server installation takes about 1.5G of disk space. With MATE it goes to 2.5GB up to 4GB for the full Ubuntu install.