First, I think the important thing is to decide for yourself what "fluent" means to you. Do you mean, able to survive in Korea and get around? Do you mean able to watch Korean programs without subtitles and understand 100% of the content? Do you mean being able to discuss any random topic in depth while expressing your opinion as much as you could in your native language? These are all very different levels of language ability that many people consider to be markers for fluency.
That being said, getting around in Korea doesn't demand a high command of the language if you speak English. As for Korean programs your best bet would be to study high frequency media vocabulary (HFMV). Most languages sit at around 2,000 words or so, but you can find more specialized subsets based off of subject matter. Let's say you can watch the news on weather (a relatively easy topic), but when it comes to economics or politics you have a less stable grasp on vocab. This is where individual HFMV subjects would come in handy. Lastly, for the last marker I mentioned...I think that just comes with usage. Read articles on topics you're passionate about, and study related vocab. Keep journals and join interests groups. Naver Cafe is an invaluable resource for this type of study.
All in all, fluency is a very difficult concept to measure due to its relativity. I hope this helped!
포기하는 말은 배추 셀때만 쓰는 말이죠! 화이팅~