I think the most important thing is to achieve your goal: to be able to communicate in English. Because you can have some knowledge of English but it can also happen that people won't understand you. I think that you first need to develop your ability to SPEAK it and to LISTEN and UNDERSTAND it. Unless,of course, your future job will not involve either of those, speaking and listening is what you mostly do when you learn another language. Then I would consider you learn to write, expand your vocabulary and improve your grammar. Getting a good teacher or studying materials is also important. And you can never forget: MOTIVATION.

I think it is speaking.Because our first purpose to learn English is communicate with foreigners.

To get the pronunciation right helps a lot to remember and communicate