How many staging environments?

We are 1+ year into production. All of our software development is outsourced. 

We currently do not have any staging environments. We have a test web site with a test database but that is it. When our outsourced folks fix a bug or add a feature they drop it on the test site and ask us to look at it. Not the best I know, but it has worked. 

I have the green light to set up a staging environment at our data center. 

My first staging environment will be for development. 

I am thinking about adding additional staging environments, like QA, Acceptance Testing and one for the sales/marketing folks to do demos.

One of my goals is to get releases to the point where we control them versus our outsourced folks pushing releases.  

What does your staging environment look like and do you have any suggestions for ours? 

Thanks