You could sneak in a 270x for $652
PCPartPicker part list:
http://pcpartpicker.com/p/3FlBY
Price breakdown by merchant: http://pcpartpicker.com/p/3FlBY/by_merchant/
Benchmarks: http://pcpartpicker.com/p/3FlBY/benchmarks/
CPU: Intel Core i5-4440 3.1GHz Quad-Core Processor ($177.00 @ Amazon)
Motherboard: Gigabyte GA-B85M-DS3H Micro ATX LGA1150 Motherboard ($55.04 @ Newegg)
Memory: G.Skill Ares Series 8GB (2 x 4GB) DDR3-1600 Memory ($68.99 @ Newegg)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive ($54.44 @ Amazon)
Video Card: Gigabyte Radeon R9 270X 2GB WINDFORCE Video Card ($199.99 @ TigerDirect)
Case: Cooler Master Elite 430 ATX Mid Tower Case ($29.99 @ Newegg)
Power Supply: EVGA 600B 600W 80+ Bronze Certified ATX Power Supply ($49.99 @ Micro Center)
Optical Drive: Asus DRW-24B1ST/BLK/B/AS DVD/CD Writer ($16.99 @ Newegg)
Total: $652.43
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2014-05-06 23:23 EDT-0400)
Or you can start the build with 4GB RAM and add 4GB more later when you get another $30-40 and get a GTX760 now.
PCPartPicker part list:
http://pcpartpicker.com/p/3FlGJ
Price breakdown by merchant: http://pcpartpicker.com/p/3FlGJ/by_merchant/
Benchmarks: http://pcpartpicker.com/p/3FlGJ/benchmarks/
CPU: Intel Core i5-4440 3.1GHz Quad-Core Processor ($177.00 @ Amazon)
Motherboard: Gigabyte GA-B85M-DS3H Micro ATX LGA1150 Motherboard ($55.04 @ Newegg)
Memory: A-Data XPG V1.0 4GB (1 x 4GB) DDR3-1600 Memory ($34.99 @ Newegg)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive ($54.44 @ Amazon)
Video Card: EVGA GeForce GTX 760 2GB Video Card ($239.99 @ Newegg)
Case: Cooler Master Elite 430 ATX Mid Tower Case ($29.99 @ Newegg)
Power Supply: EVGA 600B 600W 80+ Bronze Certified ATX Power Supply ($49.99 @ Micro Center)
Optical Drive: Asus DRW-24B1ST/BLK/B/AS DVD/CD Writer ($16.99 @ Newegg)
Total: $658.43
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2014-05-06 23:25 EDT-0400)
You could also drop the optical drive and save another $17. That another thing you could very easily add later when you get more cash.