Grammar is important, but it should not take up a disproportionate amount of your preparation time.
In most Banking Exams, a major portion of the English section tests your ability to read, understand and interpret information rather than simply recall grammar rules.
Focus more on:
Reading Comprehension – Develop the habit of reading editorials, articles and quality passages regularly. Learn to understand the main idea, tone, context and author’s viewpoint.
Vocabulary in Context – Instead of memorising hundreds of words, understand how words are used in sentences. This helps in RC & fillers.
Sentence Understanding – Learn to identify what a sentence is actually trying to convey. This improves your performance in fillers, para jumbles, phrase replacement.
Basic Grammar – Do learn the fundamentals: subject-verb agreement, tenses, articles, prepositions, pronouns, conjunctions and modifiers. But once your basics are clear, prioritise practice and application over memorisation.