Try the TOEFL iBT sample questions. This company suggests using the "five paragraph" essay structure. here's a link with the questions: http://kazuo.fc2web.com/English/TOEFL-essay.htm

Many people write about whatever they found interesting that day. For example, I wrote a notebook entry to welcome back a friend who didn't log on italki for like 2 months jejeje :D write about politics, whatever topic you have an opinion about, music you like, childhood memories, etc. Just have fun :))

write why you joined italki and what you want to accomplish.

Write about your experiences, What you good at, what you wanted to do , etc

try to write some information about your city Karachi, and also about that the Karachi is the business corner.