You might probably know, there is a Team Member license for Dynamics 365 CE which costs $8 as opposed to full user cost of $115.
You might wonder how a team member license is different from full user license.
As per Microsoft Licensing Guide, Team Member license is for
"This license entitles the user to light weight access through designated scenarios built into Team Members experience"
What you can do with Microsoft Dynamics 365 Team Member license:
Dynamics 365 Applications: full read across
Access Anywhere: Web App, Mobile App, Tablet App, via Outlook
Activities: view and edit
Announcements: view and edit
Contacts: Team Members user may create, read and update
Dynamics 365 Mobile Client Application: use (for iPad, Windows) except for Field Service
Gamification: access as a fan and spectator
Microsoft Excel: export data and access user reports, charts and dashboard
Notes: view and edit
Voice of Customer Surveys
Yammer: collaboration (needs Yammer license)
You can use up to 15 custom entities
Employee Self Serve: start personal support chat and cases and view knowledge articles (Portal or API access only)
Apply for Project, report Time & Expense for Projects, update Project Tasks, Update Own Resource Competencies for Project