I am a graphic designer. I use mac at work, pc at home. Considering your question is regarding PC, I would suggest a good quad core processor. Faster better. A haswell i7 would defiantly be ideal. Look for lowest priced i7 around you. Consider a K sku if you want to over clock, just make sure you know what you are doing. a blue screen in the middle of doing a design is tragic, consider photoshop and illustrator dosnt autosave/recover files until CS6.
Get an NVIDIA GPU, like a 760 for cheap. CUDA is utilized in photoshop and it does make a difference.
If over clocking, look for a good stable x97 board, if not, look for mid rang ($75-120).
Get a good quality PSU, you can find for under $150. target 600-700 watts.
Get an SSD for operating system, just a 128 GB will be sufficient. You can find these for under 100.
Get a mechanical hard drive for Scratch disk and saving large files.