Plan type needed for Teams

We are currently investigating Microsoft Teams as a product to use with external partner company that we work with

They require us to use External Access to federate.

We currently do not use any Microsoft Office 365 products and very little in way of Microsoft Products. We do have Active directory but no Exchange, Sharepoint, etc

What is the most cost effective way to do this? Can it work just with Teams Essentials? Do you get access to the admin center when purchasing only essentials? I've tried to review various setup guides and edition comparisons and it isn't clear at this point.

We only require chat and shared meetings at this point

Thanks!