you do need a half decent gaming pc to see this game at its best. If you've got a typical pc world family type pc then it just won't be anywhere near the level to get more than a few fps out of this game. I'm no pc buff but there's plenty of info out there regarding upgrades etc. You obviously need a new graphics card, maybe some more ram as well. If you post your pc set up ie motherboard, cpu, graphics card, ram then someone might be able to suggest a upgrade path.

Before messing with any settings close down any excess applications you may have open before starting the game.

If this doesn't help try the following:-

Remove or turn down antialiasing, this will really improve performance on a lower spec machine.
Turn down/off the anisotropic filtering
As others have said remove a few of the bells and whitsles, good ones to remove are:-
smoke and dust
cloud shadows

Finally if needs be drop the screen resolution down a notch or 2

Im running on a fully specced Macbook pro retina 15" via bootcamp but output the game to a 32" TV and find it much easier to drive with the big screen