I am not sure about how it works for others? My opinion before was to take a class first. If you are good studying alone, go for some online course. I took GMAT classes, then I am preparing on my own now. The classes are just for the sake of refreshing your knowledge on the subject. Some course providers also give a wide range of test taking tips on different topics which are helpful which is not always the case for students preparing on their own. (still now its just my personal opinion...)

But as I have started using BTG often now, I get a feeling that BTG is the best source of knowledge for GMAT test takers. If you have a limited time BTG is THE BEST. Join the 60 day study plan or other study plans available and you can definitely succeed.

There are a lot of people who have successfully combined a class and self-study. It's really up to each individual. I've taken a class and really enjoyed being kept on a schedule with the classes, homework, and CAT assignments. Classes are good for showing you approaches to problems that you will not get from the OG material. However, a motivated self-studier can pick up all these things on his/her own by using resources like this site, quality study books, etc. It's perfectly possible to do well on test with self-study. There are many paths to success, you just have to find the one that fits your needs best.

Thank you a lot for assistance.
Talking about the on-line courses - which are exactly the best for small student's budget?
And which materials can you recommend for self-study (I need appr. 600 and also want to strengthen my English)?

Thank you)

GMAT classes are always helpful, cause it helps you to keep up with your GMAT exam day with good practice and also helping you in understanding the concept. But you will need more time to devote for the classes as compared to self-study. If you are a working individual and have problem finding time for regular preparation, then go for self-study, which is what i am following. You can make a study plan of your own. there is a very good study plan of 60 days in this website. you can take help of that also. so all the best for your preparation.

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We are what we repeatedly do. Excellence, therefore, is not an act but a habit. - Aristotle

Well online I am not sure about an online course, since I have not taken one. But I have joined Grockit. Its like an online study group. Awesome till date. BTG forum greatest of all. To increase your verbal score, I suggest MGMAT guides. Best in GMAT prep. Hope it was helpful.