resolution doesnt matter - an old gpu could run eg Doom 3 on max at 1366x768 where as the same gpu will not run new games on the same settings - again RESOLUTION DOES NOT MATTER
get the best card you can afford, thats all it comes down to - bigger the better
perhaps an Nvidia GeForce GTX 770?
he's named a specific game, BF4,
OP, the problem here is that no one actually knows yet, wait till the 1st Oct and then ask the question once the beta is released. o do as above and spend what you can, what is your budget? for reference my opinion is that a 760 would be ok,