From which subject one should start preparing for GATE and for how much time a student should study on daily basis to get a good rank < 100 ?

Before starting preparation, one must analyze his/her potential and strengths. It will be a good idea to start with the subject in which you are most confident. The subject can be completed easily and in a very less time. Then, you may select next one in similar manner. Revision must be kept on for all previously studied subjects. Now the time of study depends on your IQ level and potential. Instead of planning a time duration for study, you make a strategy and plan to complete some particular task on daily basis. Getting a rank less than 100 is always tough as there is a huge competition in GATE. So, study duration must be as much as you can manage, otherwise you will be left behind the other competitors.