What should i upgrade to eliminate most pc game lag?

i play guild wars and have a 64mb geforce agp slot graphics card, it sucks really badly and i wanted to upgrade it, but i didnt know if upgrading it would get rid of most of my game lag, i have a high speed internet connection and its always good, so that aint the problem and i also have a crapy amount of ram, only 512mb, if i upgrade to atleast 1gb and a half would that make the game run faster? or if i upgrade to a 256mb graphics card would that make the game run faster?