Well, i am not essay exports, but i like to share my test experiences on essay writing.
First of all, i didn't know testbig site when i was preparing the TOEFL exam. Just recently one of my friends transferred me the site and asked me how is the site then i started to know testbig. It would be beneficial for me if i knew testbig earlier. At least i can submit my essays to testbig for free checking out.
The mistake i made for essay writing is that i was trying to choose relatively difficult essay topics to practice. Like "Playing games is fun only when you win", or "When people succeed, it is because of hard work. Luck has nothing to do with success". These kinds of essays need more arguments. It is hard to manage. and it made me somehow frustrated because i didn't know how to develop the reasons in essay body.
Actually the essay topic for my first TOEFL exam is: A company has announced that it wishes to build a large factory near your community,Do you support or oppose. The second time i took TOEFL exam, the essay topic is: Do you like to eat at home or restaurant? They are pretty easier to write, right?
The better way to practice essays is to keep balance: most of them should be easy topics while very few times would be difficult ones.
Welcome your comments if you don't agree with me.