What phisical architecture for asp.net core microservices application

Hi!
We have an asp.net core microservices architecture deployed on single Windows Server/IIS web server and we are using Ocelot as API Gateway.
We should soon make our application available to 400 users at the same time, so we're assuming it's best to add another Windows Server/IIS web server for balancing and performance reasons. 
We were first wondering how we can make web api scalable without using dockers technology. 
Then we would wanted to know how the balancing of requests should be handled, is a third node necessary? If so, the requestes could be managed with the Ocelot web api gateway or another type of product is required?

Thank's in advance for your suggestions.