FOR ISRO, do following.
1. Solve previous year of gate completely.
2. Solve previous year of ISRO
3. Study java,c++,image processing,software engineering concepts in addition.
4. Still if you got time, then solve answers of questions people are posting online like I AM DOING NOW. :) All the best .
and yaa pattern and syllabus is not same in ISRO. I think in ISRO 60% marks will be enough to crack written exam. and in ISRO exam , questions are easy and it required speed.