Life at an IIM
Hey Sameer, there's no count on how many vocabularies you need for CAT, reading should be your strength and thats it. So please devote 1 hour everyday to go through any kind of an article, preferably of different topics.
Personally, I didn't pay much attention to building vocabulary. I simply googled the meaning of any new word I came across anywhere (the most frequent source being editorials). More than vocab, I feel, you should practice understanding the meaning of a sentence/paragraph as a whole than focusing on a single word you don't know the meaning of.