Building a PC - optimum hardware considerations?

[Cloudbusting]

Hi,

I'm thinking of building a desktop PC for work and I was wondering what
sort of hardware I should invest in for an optimum and responsive
performance with Artrage.

I'm hoping to get a Wacom display monitor so I'm really hoping to make
the brushes as responsive as possible for a true-to-life drawing experience.
Aside from a decent multicore processor and RAM, is there a considerable
boost in performance with:
Ram speed - i.e. GDDR5 vs DDR4 vs DDR3?
Recommended Graphics Cards?
Is Graphic Card memory more important?

Look forward to hearing from you