System Memory and CPU are important as well. Buying a good quality graphics card for an average PC won’t do you any good. After Effects is high on system memory, including CPU, and Video card.
If you have 16 gig system memory, and more than 6mb CPU Cache than you are fine. However, recommending you a video card is absolutely critical at this point. You need to give us more information, what you currently have. Without more information it is impossible to recommend a video card for your system.