Graphics cards are important for issue-free work, however ram is very helpful especially when you hit those higher amounts of polys.
For video cards, you'll want to take a look at the Nvidia Quadros, or ATI FirePros. These are their workstation cards, which are purpose-built for things like Maya. These cards support more features of OpenGL, which is the rendering engine that Maya uses.
Gaming cards have issues with Maya; such as display problems, or even crashes.
The higher-end versions of these cards can be pretty pricey, but the lower-end are quite reasonably priced. Check the Maya qual charts and see what's qualified to run Maya: https://usa.autodesk.com/adsk/servlet...&siteID=123112
Imagination is more important than knowledge.