What games are you playing?
gta 5, arma 3 and most recently witcher 3. the main problem is the VRAM. my 650ti is a great card but if only i had bought a 2gb one..
I'm not completely aware of the prices, though 780Ti might be in that range, while still having great performance (more or less same as current Maxwell ones). GTX 960-970 are probably out of your price range (not sure about second-hand prices).
As for DirectX 12...it's a nice bonus, but it will take quite a while before games start making use of it (developers need to include DX12 support).
well yes according to my local price list, they are out of my budget range. i did a mistake buying the 650ti of 1GB, dont wana repeat the same mistake again.
second hand is never an option in regards to computer peripherals, have some bad experiences

A GTX 960 is around $220 w/o shipping fee on Amazon, ships worldwide. My guess is that it's your best at this range.
its around 350$ in my country and i cant buy from amazon since i dont have a cc. i can only buy it from my local online store with my debit card