Disclaimer: The GRE Program discontinued the Computer Science Test
I'm from an unknown school in Georgia. I want to apply for grad school in U.S, but I don't have a good GPA although I am at the top %15 of the class. Here we have some strange grading system - we use 4.0 system but grading is not similar to the western world. I am confident on my knowledge and I believe that I can do well on GRE CS Subject exam.
So do you care about or value GRE Subject test results ? If so, what score do you expect from a candidate ? Is it possible to get some funding at top 40-70 range schools? Regarding research, I don't have possibility of doing any research and it is not a top priority here, so we aren't provided opportunities for research.
The GRE subject tests are useful measuring sticks in disciplines where it's available, as they test understanding in a single discipline in a way that is hopefully "neutral" across different schools.
That said, you'll need to have a very strong overall package in order to overcome the weakness in your GPA. A strong showing on the GRE subject test will help, as will strong letters of recommendation from several of your instructors. These letters should clearly indicate structural reasons why you can't do research, and should find some way to indicate your aptitude for graduate studies. If it is possible, you should also get an official note on your transcript indicating your class rank.
I can't really comment on the funding situation in CS; perhaps one of our other site users can fill in that part of the picture.