What is a good video card for my pc?

i have an intel chipset. i am 13 years old and i am saving money to buy a video0 card which is worth 2500 pesos which is like 50 dollars i think. how do i replace the video card? when i asked the dude in the shop on what is a good video card he said the video card with the asus brand. when i asked why not NVidia and the dude said its for high grade motherboards only and i know my computer is not that. i want a new video card because my left 4 dead 1 and 2 gameplay sucks because all the walls are white. if u need more details just tell me|||you can get a gt 240 for 60.00 after rebate but before rebate it is like 80.00 for 50.00 you can get like a 4650 but please make sure you have the right slot for the type of video card you are going to get.