We have a web application that we are about to take live. But I have a fear that the server won't be able to handle all the requests and it won't be as comfortable to the users as a website should be. Currently I'm thinking about using 2 things. One of them is having 2 more additional servers and use them to loadbalance the users between the servers. So it would be 1 Loadbalanced server, 2 webapplication servers and 1 backend (database) server.
The other thing is HTTP cache. Can it be enough if I just get one more server and set it up as a cache server with NginX? Which would you do if you are limited in terms of resources and why? (Maybe how?)