hi,

see the time table should be made by your own conveniences, since there is no particular age limit for gate exam, candidates from working professional to college students appear in gate exam.

however to crack any particular competitive exam you first have clear idea of the syllabus, scoring points and easy  topics, most important topics mark out. at least devote 6-8 hours for studies, make short notes, before 3 months of exam have to attempt the mock test to get accustomed with timing and exam time speediness of solving questions. you have to select the topic which is your weakness and give extra time for preparation.

hope you understand.