Do i simply install on top of a Debian server OS? Which .iso do I download/install?

I think even XFCE is rather bloated and have Debian XFCE on 2 other drives already, so will test out Debian stable nonfree with xfwm standalone. I have the names of the top 5 packages to add and will worry about the rest later. I am in no hurry to get this perfect yet. But, I would like to install the fundamentals tomorrow.