Till oct 15 i will complete 7 out of 10 subjects in my GATE preparation. Is it enough to get a good rank if i continuously revise and give series of the my completed subjects?

Dear student,
It all depends upon your capabilities.
As you are saying that you will be completing you 7th chap on oct 15 and constantly revise those, then according to me still that is not enough for your top crack the gate. It may be possible that you have cleared the cutiff and qualified the exam but your score will not be that much to pursue you Mtech or any psu.
GATE is a national level exam where the selected candidates with good score can do the higher studies of Mtech or go for a psu job.
For a national level examination you must prepare all the chapters all the subjects. And never leave any chapters.
In gate exam engineering mathematics and aptitude section plays a very important role apart form your core chapters.
Min 30 marks are comprised of these two subjects and the cutoff is also of around 30 marks.
If you are giving the test series and practicing regularly your 7 chapters then it's good, but simultaneously go through all the other chapters.
Because in a national level examination, any topic can be asked from anywhere.
So don't leave any chapter behind. Go to the examination hall fully equipped with all the chapters and concepts completed. And give your exam with full confidence.