Qlikview Personal Edition is enough to complete Designer1,Designer2 and Devloper 1 courses.
Where and When Server Needed:
Say you have developed an application for a company. Now it is required to be shared by many people in the organisation over the (local) intranet or even internet. This distribution task and related management is done by a special software called SERVER. So if your requirement demands so(sharing aspect), then only you are supposed to be worried about server. And if you are only concerned about the development , don't worry about this server part, your personal edition QV is enough as this includes all the technical facilities as an stand alone application development environment.