Ok well this is what I'll do. I'll do a conditional IF build. Basically, what I'm posting is what you should shoot for as a minimum (if possible).
PCPartPicker part list /
Price breakdown by merchant
CPU: Intel Core i3-4160 3.6GHz Dual-Core Processor ($108.99 @ NCIX US)
Motherboard: ASRock H97 Anniversary ATX LGA1150 Motherboard ($69.99 @ SuperBiiz)
Memory: G.Skill Ripjaws X Series 8GB (2 x 4GB) DDR3-1600 Memory ($49.99 @ Newegg)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($49.99 @ Amazon)
Video Card: EVGA GeForce GTX 750 Ti 2GB Video Card ($114.99 @ Newegg)
Power Supply: Antec Green 450W 80+ Bronze Certified ATX Power Supply ($47.98 @ Newegg)
Optical Drive: Asus DRW-24B1ST/BLK/B/AS DVD/CD Writer ($18.89 @ OutletPC)
Total: $460.82
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2015-06-07 16:39 EDT-0400
Breakdown:
Start out with an i3 and an H97 (if possible). Look for 8GB of 1600 RAM, 500+ HDD, Nvidia 750/750 ti or AMD 260/260x. If possible get a 550 watt PSU that way you can support more powerful GPUs down the road. Buy a DVD drive if necessary and pick a case (I don't pick cases).
Brands:
Motherboards: Asus, ASRock, Gigabyte or MSI
RAM: There's a lot but my favorites are G Skill, PNY, Kingston, Crucial and Corsair
HDD: Meh
GPU: EVGA, Asus, Gigabyte, MSI, Sapphire
PSU: Antec, XFX, Seasonic, Superflower, FSP, Corsair (some), and EVGA (some)
DVD drive: meh.
Edit: That range of parts should get you in Medium performance. If you can get the 660 GTX, I would.