A graphics card is mostly used for 'calculated' graphics.. rather than AutoCAD.
Not all computers have seperate graphics cards.. some have 'on board' graphics.. this means the graphics are integrated on the motherboard.. this is the lowest spec. Otherwise yo'd have a dedicated graphics card.. this is seperate and plugs into the motherboard.. .. and has seperate graphics memory, as opposed to sharing memory (i.e RAM is shared). So you can have a NVidia graphics for example, with 256Mb of dedicated memory, as per my 349 Harvey Norman laptop. The 527 Euro Dell laptop, from Harvey, had on board graphics, with only 32Mb of dedicated memory.
(The 527 laptop had 4GB ram, and 500GB hard drive, and a webcam, and perhaps a better screen, and a better processor, but not worth 1.5 times the price of the 349 laptop I bought... graphics are worse on the 527 laptop)
So games need a good graphics card, but AutoCAD may not. (AutoCAD may use the graphics card to do 3D modelling and rendering, but this isn't 'real time' work, so it's not a problem to wait 2 mins for a complex 3D rendering to happen)
Games need grapohics for shading and textures etc.. the games still play without these extra featres... but perhaps the experience is slightly lessened.. similar to having 'normal' sound, or 'explosive 6 channel sound'. Will you miss this if it's not there?...
Screen resolution may be more important... 1,920 x 1,200 wold be close to the max... whereas 1,368 x 800 would be the lowest you're likely to see. The screen can be a little cramped at the lower resolutions due to the number of buttons and commands.
(The 349 laptop I bought has 1,366 x 768 resolution.. pretty low, but the laptop would handle an external monitor of greater resolution.)
Any of the modern laptops will work pretty well for normal use and for light AutoCAD.. it's not really necessary to buy the most modern and expensive type.