Hello Kony,
It's nice to answer your question.
Actually, some TOEFL courses are expensive but some are not, like the summer TOEFL courses in a few univesities.
You can do many things to strengthen your English too like by conducting self-study yourself. In this way, use search engines to find out about TOEFL and what you should do, or ask someone who has ever taken TOEFL. Actually, google 'TOEFL' and find lessons/instructions about TOEFL online too.
www.google.com. Morever, busy a few TOEFL books which provide you more information about TOEFL. It can help.