Your goal should be to learn the Standard American Accent. Some people call it “broadcaster English.” It’s the kind of standard, neutral speech you hear on CNN for example. It’s a non-regional American accent, meaning that people don’t associate this accent with any particular part of the United States. This is the accent that I teach.
Some people have opinions about accents that are non-Standard Americans. People from Brooklyn or Texas or Georgia all have a certain way of speaking. Some dialects can be charming and others rather annoying.