This blog post shows a few ways in which you can easily crack IIT JAM MS in the very first go ...
1. Sequence and Series - One and the only resource for this entire topic is "Introduction to Real Analysis" by SK Mapa. You don't need any other resource . Just go through Chapters 5 and 6 extensively. By this I mean that you need to go thouroughly through these chapters 4-5 times until all the doubts are cleared. The questions in the IIT JAM are not going to be straightforward, you need to extremely clear in terms of the basics to solve these questions. So, try to follow the given approach and start to solve the questions in the JAM exam one by one.
2. Differential Calculus - This was the topic that I found the most difficult after Integral. If you want to be absolutely confident with this portion, this is the perfect resource. Just go for GB Sir for Limits, Continuity and Differentiability .(You can also find his lectures on youtube for free). He teaches these topics for JEE Mains Students, but trust me if you go through his lectures and complete the course, there will be absolutely no question in Differential that you won't be able to solve.
For practicising Differential, just go through the notes of GB Sir and solve limit questions from "A Problem Book in Mathematical Analysis" by GN Berman. And ofcourse, nothing beats the previous years of IIT JAM as well as JEE Mains(for this topic only).
3. Integral Calculus -For me, this was the most difficult topic to prepare. So I started with GB Sir's videos on Integration. This will give you more than enough knowledge about integration in order to solve the questions. Also focus a lot on "Lebnitz's rule". The formula is pretty simple, just look for the formula on google and try to understand it completely.
For practicising, I just practised through GB Sir's notes and previous years.
4. Linear Algebra - Youtube will be your best friend for this topic.If you want to study in Hindi, you can surely opt for Dr.Gajendra Purohit and for English go for Gilbert Strang for Linear Algebra
For practicising Linear Algebra, try solving the questions from previous year exams of IIT JAM MS, IIT JAM Mathematics and CSIR NET. There are also videos on youtube solving 50-100 questions from these exams .These are going to be more than enough for you to practice. No need for any seperate book whatsoever.
Statistics
1. Probability - One of the most scoring and easiest topics which is asked in IIT JAM MS is Probability. You should always start with the chapter 3 and 4 of FMS. But if you feel that you lack the confidence to solve those questions start with the NCERT Maths book of class 12th. Chapters will seem to be very basic and they are but still make sure you go from the 1st to th Miscalleneous exercise. The questions asked in IIT JAM won't be tougher than the ones in Misc. Excercise and the ones present in FMS. Trust me, doing all this is going to take a good one week period but your confidence will be through the roof atleast for probability.
2.Distributions - The book for these topics are "Introduction to Mathematical Statistics" by Robert V.Hogg and FMS. This book is a very easy read and covers basically everything about this topic. After you complete this book, come back to FMS and solve the questions there too. You see how much things are easy/difficult for you once you will try the examples in FMS.
Note - You don't need to solve the exercise questions in FMS.They will just waste your time
3.Inference - Inference is one of the most interesting topics for IIT JAM. In terms of books, "Casella and Berger" should be your starting point for Inference.Next book you should read is "An Introduction to Probability and Statistics by V.K. Rohatgi"(specifically for Inference). You can go through my notes of Inference, they will surely give you deep insights into Inference.
Even if you think that you know nothing about inference, you can surely refer to my notes; they are going to be extremely useful for you in your JAM preparation.
Other topics in Statistics - The above mentioned topics are the most important topics that you need to cover in Statistics.The ones which are left like(Ordered Statistics, t- distribution, F-distribution) can be easily covered from FMS. Don't worry FMS is more than enough for clearing IIT JAM. If you just focus on clearing your basics from FMS and solving the examples again and again, within 2-3 months you will be extremely confident in Statistics.
Additionally,
For Statistics, even though I have mentioned a lot of resources ,if you ask for only one resource then that would be FMS. Keep it as your first priority. You need to practice FMS atleast 8-10 times in order to be sufficiently confident with the questions. Mathematics isnot neccessary to clear the IIT JAM exam but is extremely recommended because although it won't give you a lot of marks, but it will increase your confidence in the exam entirely. I would highly recommend you to check out GB Sir for the above mentioned topics. It will take you sometime, but that will surely be beneficial to you during your final exam. In the end, practice is the key to solving the final exam. No resource will beat the power of previous year question papers. The strategy that really worked for me is "Correct strategy to practice the Previous Year papers for IIT JAM exam".