Should get well over 50 fps on modern games, under 600 dollars, and if you want a mouse/keyboard/headphones added just say so.
PCPartPicker part list:
http://pcpartpicker.com/p/NRHHHx
Price breakdown by merchant: http://pcpartpicker.com/p/NRHHHx/by_merchant/
CPU: AMD FX-4350 4.2GHz Quad-Core Processor ($89.89 @ OutletPC)
Motherboard: Gigabyte GA-78LMT-USB3 Micro ATX AM3+ Motherboard ($44.98 @ Newegg)
Memory: Team Elite Plus 8GB (2 x 4GB) DDR3-1600 Memory ($34.99 @ Newegg)
Storage: Team Ultra L5 120GB 2.5" Solid State Drive ($39.99 @ Newegg)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive ($44.89 @ OutletPC)
Video Card: EVGA GeForce GTX 960 2GB Superclocked Video Card ($170.99 @ NCIX US)
Case: Antec NSK4100 ATX Mid Tower Case ($34.99 @ NCIX US)
Power Supply: EVGA 430W 80+ Certified ATX Power Supply ($15.98 @ Newegg)
Optical Drive: LG GH24NSC0 DVD/CD Writer ($13.89 @ OutletPC)
Operating System: Microsoft Windows 8.1 OEM (64-bit) ($87.98 @ OutletPC)
Total: $578.57
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2015-11-05 12:05 EST-0500