ps2 emulator requirements.help

hi guys! i have ps2 emulator and everything it needs like dvd games and bios files but i cannot play games on it. but my pc RAM is 512 mb. and my friend told me that u must insert another 512 RAM so that it becomes 1024 RAM. ok i agree with that but he also told me about a card called AGP card that will make ur ps2 games play on pc. but another guy told me that u must buy VIDEO card. now i am confused so if someone is playing ps2 games on pc. can he tell me what should i buy and what should be my ram.please reply.thnx