GATE

There are two things –
One, you want to clear GATE and second you want to score a good rank. For No.1, just Study for a month from any Xyz BT book.
For No. 2, you have to follow a long and laborious path, I think 6-8 months are necessary for GATE prep. Just make proper time schedules, undertake regular test and study regularly
Now coming to the books
The wonder and magic book - Biotechnology a problem approach by pathfinder academy (don't make a mistake to overlook this book.)
The above book is though sufficient in many ways but to score a rank of 30 or less from a rank of 200, you need to carry extra. Alongside pathfinder read standard book of every subject i.e. Kuby, Prescott, t a brown, Doran, Shuler, Whittaker, Alberts and all the standard books of subjects that you have read in these 4 years of engineering. The other books that you would require is Maths, sample paper and previous year solved question books of pathfinder academy. Believe me these would be sufficient and it might sound much but once you start preparing through them, they would become doable and necessary. All the Best.

Hi Vinoth have a look. How to Prepare for GATE 2019 Mechanical Engineering (ME).
GATE is a national level examination which is considered a tough nut to crack. Students take on various study methods while preparing for the examination. Some of the preparation methods have been listed out to give that extra boost to the candidates. Make sure you know your syllabus before starting off with any studies, it is important for the candidates to know their syllabus. Candidates should check their official syllabus of Mechanical Engineering (ME). Early preparation is the key for success. The earlier the candidates start their preparation, the better it is. This will give the candidates time to study all of the topics properly with additional time for revision. Check all important study materials while preparing, the candidates should use all of the important books and study materials. By preparing using the books, the candidates will be have higher chances of doing well in the examination. Solve Mock Tests and Sample Papers Candidates are advised to solve sample papers and mock test during their preparation process. This will allow the candidates to practically apply what they have studied and check their mistakes so that they can rectify it. Previous Year GATE Syllabus for Mechanical Engineering (ME)
Since the syllabus for Mechanical Engineering of GATE 2019 has not been released yet, the candidates can refer to the previous year syllabus. The GATE syllabus will be updated as soon as it is released by the official authorities. Hope this will help you. Best of luck.