Wait, you're asking for a GPU that will enable you to take advantage of game glitches and basically cheat? Then when told you don't even have the CPU to do it, even if you had the GPU, you ignore the people who obviously know more about this stuff than you do because you are here asking in the first place.
Get a better system, like an i7 2600K and a worthy GPU like a GTX 1050. That will be enough power for you to cheat at that old game. Who knows, you might even find a newer game that is fun to play without cheating.