Hi, I have known people who have got excellent scores by spending just four hours a week on their test preparation. In the end its about the quality of time and not the quantity.
I would suggest you join a study group or a similar setup with those who are well aware of the GMAT format. Your time investment could be minimum but you will get alot more out of it than trying to do everything on your own. It is best to be well prepared before you sit for the exam as it deals with your future career at the same time, it can be done wisely with optimal time managment as in your case.
I have heard Princeton review
has weekend classes in their centres all over India. See if you can join such classes. They are indeed great help for timely challenged. manya education site for your reference.
can anybody help me out with the time that i need to invest religiously to get a good GMAT score. I am currently in an IT firm and can invest only 1hr on weekdays and 5 hrs on weekends.