The more effective way is to choose a textbook with moderate difficulty and good arrangement style, read the text carefully, write down all the new words, find out the corresponding meanings and example sentences in the dictionary, and record them in the notebook for easy review and memory. Or if the textbook itself is well compiled, there may be detailed English-Chinese definitions and example sentences in the vocabulary behind the text, such as New College English compiled by Zhejiang University, which is very helpful for improving reading and suitable for self-study. I personally recommend it.
As for listening, listening extensively and repeatedly, and being exposed to a lot of listening materials, will certainly gain something. Listening comprehension of TOEFL and IELTS is more difficult than CET-4 and CET-6, so it is suggested to strengthen listening and speaking before the exam. Of course, words are still very important, but we should remember them flexibly in various forms of learning. As long as you are interested in English culture itself, it will be easier to learn, but targeted training is still necessary.
I used to get 90 points in CET-6 100, and I think I can get more than 7 points in IELTS (although I haven't taken IELTS, I have taken BEC Advanced Test). The above personal experience is for your reference.
As for phonetic symbols, you can pay more attention when learning words. If you are not familiar with phonetic symbols, you can make up one specially. It is also easy to make a surprise attack. This is a problem accumulated in the future.
You can learn new concept English 3 and 4 in summer vacation, although they are relatively old textbooks.