Hi Yukiko,

As you want to do exam English lessons, I would strongly suggest looking for teachers with that experience in particular. The IELTS is not just an English exam but its also an exam that checks your ability to succeed in an English speaking academic environment. 

Both professional and community tutors are fine as long as they are aware of what the examiners are looking for.

I find that my most successful students are happy to self-learn with the materials I provide, and do lessons once or twice a week where we review common errors they make and strategies to pass the exam.

Hope this help! Good luck with your IELTS preparation! 

Since you already have a book that you want to study from, I think you can go with either, depending on *how* you want to approach the class. If you want to go through the textbook chapter by chapter with someone, then a professional teacher might be better for you. If you plan on studying on your own, but would like someone to answer your questions or help you review concepts after you've studied them, then a community tutor would work. Roughly speaking, if you don't need the instructor to prepare things in advance for you, then a tutor is sufficient.

In either case, you should try contacting the instructors you're considering and explain what you would like to do so they can propose a method/approach, and see if their style of teaching suits you.