The best HDD's to go for are Seagate and Western Digital. In my most recent build I went for the Seagate Barracuda SATA 6Gb/s 1TB Hard Drive. If you plan to overclock you will need to buy an after market CPU cooler, otherwise the stock one will be fine. Regarding the RAM, Corsair, G-skill and Mushkin are the brands I reccomend. No more than 8GB is needed. Make sure it is compatible with your motherboard and CPU. As for video/graphics card, I would go for XFX 7850 or Sapphire 7850. As for PSU, 500W is what you should get. You probably don't want an expensive case so I've given you two options, one a mid-range, other a low-end. The low end is the In-win Griffin and the mind-range is the Zalman Z11 plus. As for the motherboard, ASUS or Gigabyte. Make sure it includes USB 3.0. Optical drive: Not that expensive unless you want blu-ray. Suggest a DVD-RW. Monitor and peripherals I leave up to you. Don't skimp on the power supply.
Here is a build I would suggest:
Intel Core i5 3570K (Ivy Bridge)
G Skill 8G(2x4G) DDR3 1600Mhz PC12800 RL 9-9-9-24(CL9D-8GBRL)
Zalman Z11-Plus Black ATX NO PSU 4x120mm FAN (overpriced on umart)
Antec VP-550P 550W Strictly PSU
Sapphire HD7850 2G.2G 256Bit GDDR5 PCIE3.0 DVI HDMI 2*MiniDSP DX11
I've left out the motherboard and hard drive for your choice. The cost of the items listed above from umart is $742. The case can be found cheaper. This is just a guide. Hope it helps. If you have anymore questions then just pm me.