I usually advise people to invest time and money early on for pronunciation. As you learn words and phrase after mastering Hangul alphabet, you might want to find a good teacher, books or websites that can teach you the basic sounds in Korean so you get a good foundation to build on. I believe having a firm grasp of the phonetics at an early stage helps you tremendously later on. And this understanding is difficult to gain on your own.
Beyond the pronunciation you can do most learning by yourself, although taking courses and interacting with Korean speakers would be helpful too. The most important thing would be the desire and will to keep doing it regularly, with high enough concentration and without stopping for long periods.
For learning methods, my belief is that the traditional text, vocabulary, and grammar-based way is still the best if not the only way to seriously learn a language. Other activities are mostly peripheral and only help in stoking up your interest and in giving feedback on your learning. Reading good texts and listening to appropriate audio materials while looking up vocabulary and grammar as necessary is the essential activity of learning because of several reasons.
It is a pure and efficient way for the serious learner because one is not distracted with non-essential things (nice smile of an actress, breathtaking scenery, funny joke, et) in most other media. All such things are designed for diversion and enjoyment, going for witty and slangy language to interest the native speakers rather than correct and clear one for learners. Native speaker friends are largely the same - they don't exist to help you study unless they have been hired to do that.
In short, to be competent in two years you'll have to study really earnestly much like a college student taking primarily Korean courses. All those "easy and painless" methods you hear about all the time are the language version of snake oils in my opinion.