Traditional grammarians have always maintained that the past perfect tense must be used when the time of one past action is more past than that of another. Sometimes we can use time conjunctions (e.g. before, after, when, while, as soon as, no sooner etc.) to talk about two actions or events that happen one after the other. Usually the past perfect tense is not necessary in these cases, though it can be used.
The best way of approaching the IELTS speaking test is to use your 'natural' speaking skills. That means you don't have to learn any particular skills just for the sake of doing well on the IELTS speaking test.
