how can I improve my VA/RC section?

You can firstly refer to books by Arun Sharma for Verbal Ability. Word Power made easy is another great book. It is also recommended to have great comman over English which would only come by reading self help books, Financial newspaper and News channels like Bloomberg, ET Now, CNBC Bazar. For indepth preparation check below:- Always follow modern day Bottom Up approach to understand views of the author, and tone of passage where questions are read first and then the passage. Then you should summarize the passage thoroughly and eliminate all wrong options. For almost similar options select yhe one which fulfills the question requirement more and for that you need more and more mock tests and analysis of the approach you have. For complex passages, it is recommended to go for book named 'word oower made Easy' to understand all jargons and Different synonymous words.

Be an avid reader....For RC, start with something that you are interested in(don't bother about the topic)...learn to skim paragraphs and do so similarly while you are reading a newspaper/novel as well, basically make it a habit...For VA you will have certain rules that you can easily find out over the internet which you need to practice to become proficient at it

For the verbal ability and reading comprehension part you have to most importantly get accustomed to the questions that are asked in the tests. There are a number of books that are available online that you can buy. Solve all exercises in those books.  It will give you an idea of how to approach such questions. Read a lot of stuff. It is important to increase your reading speed. Reading a lot will help you read and comprehend difficult passages in a shorter time. Register on online preparation websites like oliveboard, test funda etc where you can customize your tests and practice.

Practice is the key to these things. Practice as much as you can and give as many mock tests as you can.

The best way to improve this section is to read and write as much as possible. Read atleast 2 English dailies and magazines like Outlook, Frontline etc. In order to improve vocabulary, refer to books like Word Power Made Easy by Norman Lewis. Now coming to the practice part, take sectional mock tests regularly and get them checked and analysed by experts.

Read the following article:

How to Prepare for Verbal Ability