Hi essprsodose,
The recent versions of the Official Guides (GMAT2015, GMAT2016, GMAT2017 and GMAT2018) are all fairly similar to one another - although a 'block' of questions is filtered out/replaced with each iteration. As such, having one copy of any of those books means that you likely won't need any of the other versions. That having been said, most Test Takers study with a variety of practice materials, so you will almost certainly need more than just one book to hit your score goal.
Since it sounds like you're just beginning your studies, then it would be a good idea to take a FULL-LENGTH practice CAT Test; you can download 2 for free from
www.mba.com (and they come with some additional practice materials). If you want to do a little studying first, so that you can familiarize yourself with the basic content and question types, then that's okay - but you shouldn't wait too long to take that initial CAT. That score will give us a good sense of your natural strengths and weaknesses and will help provide a basis for comparison as you continue to study. A FULL CAT takes about 4 hours to complete, so make sure that you've set aside enough time to take it in one sitting. Once you have those scores, you should report back here and we can come up with a study plan.
I'd like to know a bit more about your timeline and goals:
1) What is your goal score?
2) When are you planning to take the GMAT?
3) When are you planning to apply to Business School?
GMAT assassins aren't born, they're made,
Rich