When considering specifications for a computer build, begin with the intended purposes of that computer system. This will help a builder decide what the minimum specification should be for each system component.
For the graphics component:
If the computer will have low graphics requirements such as web browsing and office applications, then any compatible graphics card should suffice. Consider re-using an older card; or if buying new, something like a Radeon RX 550.
However, if the computer will be used for several years for high-end gaming on a large monitor with high resolution, then a recent model high-end graphics card is advisable, such as a Radeon RX 590 or Radeon RX Vega.
There is a lot of discussion about having a computer that is not 'bottlenecked', meaning that the specifications of CPU and GPU are balanced in such a way that neither processor is waiting on the other to do work. Although this should be considered second to the intended purpose of the computer, this is a sensible concern, as the proper balance leads to maximization of efficiency and performance per cost. This is a more extended topic that requires more specifics about which applications will be used, and examining benchmarks for those applications with the hardware under consideration.
