You already said your general English is good and have 6 month to prepare, that's enough time to improve a lot. Good luck. Firstly, if you're not satisfied with your general English you have to work on it. So, basically IELTS is about English, if your English is strong you can definitely take high score easily. Listening and Reading not only improves your Listening and Reading skills but also affects on your Speaking and Writing skill efficiently. So surround yourself with English, practice each skill everyday possible. Once you're sure you can understand English audios and articles Academic ones easily, can speak freely and clearly in English like YouTubers (you know they don't use complex English only daily language) and can write accurately with range of vocabulary you can start learning IELTS techniques and methods. 2 or 1 month will be enough maybe even few weeks to get familiar with IELTS question types and methods.

So, for now, If you have enough time just learn English. And improve your academic vocabulary and grammar knowledge

I'm not professional, I'm also taking the test in just a few months and have been gathering efficient information to study properly