Band 7 + Vocab is an app that has a small vocab list that can boost your score from 5 to 7 in writing, reading, and speaking. These words are also helpful for your listening. We have reviewed many old papers and found that students are trying to learn difficult words and forget simple words. As per our understanding, to crack IELTS you need simple as well complex words.
Try to learn these words and you will surely get 7+ scores in your exams.