For graphic design, amount of RAM will have a much bigger impact than the graphics card. 8 GB will get you through most learning scenarios as long as you're not working on very large raster images and...
Here is a mockup of one we are making (currently under production) for a ranch in Texas.
Its a tiresome process. Had to get the trailer painted by a company that actually understood the design considerations.
For the observant, youll see that the design is higher on the left side than the right. We actually measured the tilt on the trailer once its up on their trucks and accounted for that---the design will look like a straight field once the trailer is on the road.