Well, seeing as GTA5 won't be released for seven months, we have no idea what video card you'll need to play it. It's a safe bet, however, that it will be at least as demanding as GTA4.
Also, I hate to break it to you, but you need more than a video card upgrade to play new games. 2GB of memory isn't nearly enough. You'll want to upgrade that to 4GB as well.
So, I'd recommend upgrading your memory now (your computer will become much more enjoyable to use, less stuttering especially when switching between applications) and save up for a video card closer to the GTA5 release. By then, we'll know what kind of card you need, and prices will probably have dropped too so you'll get more for your currency.
With a budget like that, you can't get a GFX that meets your needs.
You need to step up 20.000 - 30.000 rupees
Really, so he need a $500 GPU to play GTA5? That's absurd.
While your numbers are in the stratosphere, the point stands. I'm really sorry dude, but 4000 rupees isn't going to buy you what you want. You need to, at minimum, double your budget. A 4000 rupee card will not play GTA5.