It depends how many FPS you want here is a comparison since AMDs latest driver update (this added huge performance in this specific game)
nte these are average not minimum FPS.
the above is average fps not minimum. your likley to get a bounce when you hit 30 which will drop you under. as said medium high is where you want to be the game will still look good so dont worry to much... best things to leave on high is mesh detail and textures everything else on medium or low. make sure you turn blur down to minimum and use low fxaa and post processing.