all my IELTS material in the link below (scored 8.5 first attempt). Please note that I am highly proficient to begin with. Therefore, if you aren't very confident, do refer to Youtube videos. Additionally:
1. ieltsliz is a great website
2. Study with a partner who's at a level above you preferably. Guided the missus and she scored an 8.5 as well.
3. Practice. There's no way to avoid this - One test a day or if it's on weekends, at least two tests a day.
https://drive.google.com/open?id=1STnaywnlpzcJW2LIl3Kuvjctm4NgWTUv