A good way to improve your writing is to work on your grammar and vocabulary systematically.
For instance, in your post, you wrote "I wonder how I scored so less in Writing". In fact, it should be "I wonder how I scored so low in Writing". That shows you haven't mastered the system of English grammar yet. Things like this can be picked up by IELTS examiners very easily, so you didn't get the ideal IELTS result.
Talking about resources/materials, you may be interested in my new book which can be found on Amazon's Canadian website now. It's called "26 Strategies to Succeed in the IELTS Test".
That's OK, Rukshesh. I did the IELTS test myself in order to figure out how to teach my IELTS students better, and my IELTS result was 9
Another way you can improve is to get someone to correct your essays for you and give you feedback on your essays so that you can write better in future. Hopefully this helps!