We have used SP 2010 Foundation edition for a year, so I am quite new to SharePoint.
Mainly it is used for transferring registries from Excel's to SharePoint lists in order to add workflows, and other out-of-box SharePoint Foundation functionality.
Now we see, that in order to move with document management, we would need SharePoint Server version - to use document sets, managed metadata, out of box approval workflow etc. So I am responsible for business case preparation.
As I've been working with IT for more then 10 years, I strongly suggest to buy one more SharePoint server license for creating a test environment. I guess everybody understands why test environments are needed in general - reduce many different risks from contingency to security.
But what would be main reasons to have it for SharePoint? For example, why wouldn't it be possible to create just another Site Collection on the same server and test stuff there?
Also what about Managed Meatadata - is it possible to have "production" and "test" metadata on the single SP Farm?