Similar questions a GUnit: Do you have the OS? Case? Optical drive? Peripherals?
Assuming you have the first on that list, I propose something like this:
PCPartPicker part list
CPU: Intel Core i5-4440 3.1GHz Quad-Core Processor ($189.98 @ SuperBiiz)
CPU Cooler: Cooler Master Hyper TX3 54.8 CFM Sleeve Bearing CPU Cooler ($20.70 @ NCIX US)
Motherboard: ASRock Z87 Extreme4 ATX LGA1150 Motherboard ($151.98 @ SuperBiiz)
Memory: G.Skill Ripjaws X Series 8GB (2 x 4GB) DDR3-1600 Memory ($57.99 @ Newegg)
Storage: Crucial M500 240GB 2.5" Solid State Disk ($144.95 @ Amazon)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($59.99 @ Amazon)
Video Card: MSI Radeon HD 7870 GHz Edition 2GB Video Card ($149.99 @ Newegg)
Case: Silverstone RV03B-W ATX Full Tower Case ($149.99 @ Amazon)
Power Supply: XFX 550W 80+ Bronze Certified ATX Power Supply ($59.99 @ NCIX US)
Optical Drive: Asus DRW-24B1ST/BLK/B/AS DVD/CD Writer ($16.99 @ Newegg)
Total: $987.55
I don't think you need, care, or want an overclocking CPU, so why pay for one? An i5 stays plenty strong at stock clocks for a while. Even more serious titles like BF4 and Crysis have a hard time pegging out a "slow" i5. However, I like adding in a simple aftermarket CPU cooler because they tend to be quieter than the stock units. And even if you're not OCing, Z87 mboards typically have some more friendly features, like forward facing SATA slots, eSATA ports, S/PDIF, and more USB ports.
I think you can fit an SSD in this build, and I'd highly recommend you use one. A 1TB drive should be enough storage for some casual gaming. However, if you need more space, a 2TB drive isn't much more.
Graphically, a 7870 is well above a mainstream card, and if you want to save a little money, go down to a 7850. Yes, you could probably game just fine on a 7790/7770, but a 256-memory bus and the added beef of the 7870 will stay strong for a while to come and I think is worth the cost. The 550W PSU has the cables and capacity to run it just fine, and will run just about any single card you'd care to throw in here in the future.
A computer case is mostly about personal preference. The Raven is my current favorite case. It's quiet and it's very good at cooling. However, it's also $150. Antec, Corsair, Fractal Design, Lian-Li, NZXT, and Silverstone all make fine cases. If you don't like this one, look at some other models and grab whatever you'd like to fit in your budget. Dropping money here would be a nice way to maybe up your SSD or HDD capacity.