As my weakest part is writingI I created a collection of Ryan's essays and letters to festern the learning process of cohesive phrases and expression using LingQ system.
There are tones of expressions that will make your writing more natural.
http://www.lingq.com/learn/en/store/81252/ - a link to Essays collection
http://www.lingq.com/learn/en/store/81253/ - link to Letter Collerction
If you need information about writing part of IELTS I suggest you to visit: