you wouldn't able to upgrade much with that budget Dost
Yet here are some options if you can put little more onto that budget(You can sell your gpu and psu and make money out of them to buy new instead)
Below are 3 gpus(according to their performance chart) and if you get the better performance one cheaper than other, go for it.
7850 > 650ti > 7770.
If you can't afford the 7850 2GB model, get the 650ti.
Next is your psu. You need at least 450watts.
You can get Corsair VS450 instead if any cheap psu.
I don't want to recommend you to buy from online, as you know how high their prices are on indian online websites. So, find a retailer and you can get much cheaper than from online. Good luck