Ayush, because we have already discussed 'how late' depends on your thinking, we shall skip that part and help you with improving your Verbal Ability and Grammar section. In Verbal Ability session, command on your English, Grammar, Vocabulary, Understanding of the given paragraph are of more importance. Reading English NewsPaper will also help you in your preparation. Read articles from time to time. Follow newspapers, magazines, and watch the news channels and browse the internet to keep yourself updated. You will need a lot of reading to help you in the comprehension section. You will need speed to help you in this section and you can achieve that only by thorough practise and reading. Take time to understand the question because most answers are interlinked.

Books that might help you are:

Word Power Made Easy (by Norman Lewis)
This is the go-to book to improve your vocabulary. It is not a book to be read but a book to work with daily to enrich your vocabulary.

High School Grammar and Composition( by Wren and Martin)
It is a very good book for people who want to improve their grammar skills. It helps to understand and conceptualise different aspects of grammar and it is a must have book for anyone with poor grasp on verbal ability or who wants to make up with the basics of english.

Hello dear

Yes definitely it is good to start from today ,it does not matter that in which age you are  .

As early you start, you will learn early that's all and I think according to your age you must be in your graduation year and after graduation you will give banking exams so start your preparation without any other thoughts and forget about the past.

You have enough time for the preparation and if you keep yourself regular then you will soon prepare yourself for the competition .

You are not late even some people starts at the age of 22-23 I. E after graduation. So don't worry at all.

Good luck