It depends on why you are trying to learn Arabic. If the goal is to understand quran then standard arabic is going to be your goal. If you want to be able to read arabic text (documents) then it is using standard arabic. If you want to go to arab country except Morocco, Algeria and Tunisia and talk in a way that people will understand you then learn Egyptian dialect. It is the de facto standard dialect due to the media and the fact that about one from each Arab speaker is Egyptian. Then to understand other dialects you will get it by living or engaging with their speakers a little bit while they would be happy to talk sometimes in standard Arabic or Egyptian dialect themselves.

Also Egyptian Arabic tends to be the easiest dialect to learn for a beginner. It makes pronunciation much easier than i.e Iraqi dialect.