Computer Hardware Question?

My computer has a 210 Nvidia Video card The Lates From the 2000 Series anyways some of the games run good some of then runs a little crappier, Jerky,Frezzing and etc. so i have 2.80 GHZ and 2.00 RAM..do i need RAM to Make it run Smoothier ? or just Ghz ? or its the same? answer now :) i have the money in my pocket ;)