good recommendations above.
I'd add an SSD, 256GB if possible (around $160). I've found nothing that makes a PC feel fast as an SSD. HDD are ancient slow things, but good for bulk storage.
Initially, I thought I wouldn't be interested in o/c, but glad I went for an o/c CPU and mobo as I feel I get 30% more performance for almost nothing! You can stick to stock clocks now, then when you need more grunt in 2-3 years, do an o/c.
If you are not o/c'ing, then any cheap mobo will do, otherwise Z77/87 for intel CPUs.
I would suggest a better GPU for any decent gaming. GTX 760, 770, 680, HD 7950, 7950, R9-280x. Or dual GPU eg. 2x7950 for a big over $400 exceeds Titan, R9-290x, 780ti performance.
Dual GPU needs two PCIe 3.0 x8 slots (preferably) with 2 slots between them ie. a ATX board, not uATX.
It's best to get an overated PSU, particularly if considering o/c on GPU/CPU as you don't want it running near max, hot and noisy. Calculators online.
I7 expensive not required for gaming, only for video rendering, complex multitasking etc.
AMD CPUs generally cheaper for similar overall performance, but tend to offer less performance for single threaded apps and are less efficient, use more power and are hotter.
hope that gives you some ideas.