Put as much money as you can into the graphics card, this will be the most vital point of the gaming computer. GTX 770 is a good choice, if you're feeling adventurous you could get a 680 and install the 770 BIOS on it for near same performance.
If you're solely going to be gaming have you considered AMD alternatives? Much cheaper, and admirable performance for the money. The 4670k is more powerful yes, and you may notice a 1-2 fps difference between the two processors, so it's your choice, if that difference is breaking point (Basing this off actual game tests not benchmarks as they may not be as reliable). If in the future your expecting to start CPU intensive tasks go with the 4670k instead, there is a major difference between the two brands at that point.
You're kinda in a bad time to upgrade at the moment with the z97 chipset coming out as well as the Maxwell architecture for the nVidia GPUs, meaning prices are going to be at a premium.
What are you're current specs on the PC?
Would a simple upgrade be adequate until you have enough money to get something like the z97 mobo, 4670k and a GTX 770?
