Minimum Server Requirement:
You can start with the standard azure plan.
Azure App Service – Production – S1 plan (1 Core(s), 1.75 GB RAM, 50 GB Storage)
Database (Basic Plan (5 DTUs, 2GB))
Concurrent User Supported with this plan: Approx 200 concurrent users will be served.
Note: Based on traffic, you need to scale up the plan.
Pricing Calculator: https://azure.microsoft.com/en-us/pricing/calculator/