The question is, which type of English is around you/in your country? The people you will talk to or write to, which type do they use?
If you are in a country that has a historical connection to the UK (India and other south Asian countries, Malaysia, Egypt, Kenya, Western European countries, etc), my advice is to focus on British English. If you are in a country that has more of a connection to the US (Japan, South Korea, perhaps most of the countries of Latin America), my advice is to focus on American English.
If you are from a country that has few historical connections to either variety (much of Central Asia, perhaps), think about which variety your listeners will mostly speak.