$750 gaming rig budget, no clue what I'm doing

PCPartPicker part list / Price breakdown by merchant / Benchmarks

CPU: Intel Core i5-3450 3.1GHz Quad-Core Processor ($179.99 @ Amazon)
Motherboard: ASRock B75 PRO3-M Micro ATX LGA1155 Motherboard ($77.55 @ Newegg)
Memory: Corsair XMS 8GB (1 x 8GB) DDR3-1600 Memory ($26.99 @ Newegg)
Storage: Seagate Barracuda 500GB 3.5" 7200RPM Internal Hard Drive ($52.99 @ NCIX US)
Video Card: Asus Radeon HD 7770 GHz Edition 1GB Video Card ($156.97 @ CompUSA)
Case: Thermaltake Armor A30 ATX Mini Tower Case ($93.99 @ SuperBiiz)
Power Supply: CoolMax 500W ATX Power Supply ($21.99 @ SuperBiiz)
Optical Drive: Asus DRW-24B1ST/BLK/B/AS DVD/CD Writer ($16.99 @ Newegg)
Operating System: Microsoft Windows 7 Home Premium SP1 (64-bit) ($89.99 @ CompUSA)
Total: $717.45
(Prices include shipping, taxes, and discounts when available.)

This is your small case, it's going to be a very tight fit!

At 750 you'll probably want to go for a gtx660 and an i5-3570K. That'll be most of the budget, but you should be able to put the rest together with what's left. You can't really go wrong with these two.

^ Wouldn't trust that PSU,

Check out my $650 build here:
http://www.squidoo.com/electronicandmore#module14669582...
Swap the motherboard with this one (-$15)
http://www.newegg.com/Product/Product.aspx?Item=N82E168...
Swap the case for this one (-$20)
http://www.newegg.com/Product/Product.aspx?Item=N82E168...
Total: $585

Save money and still get some pretty solid performance. The FX-6300 is a great chip and for what you stated you wanted to do it'll be perfectly fine. The 7870 is a great card, much better than that of the 7770 and will be fine for any modern game at 1080P max settings with no AA/AF. So it'll be solid, all with a small form factor.

FX-6300 review:
http://www.techspot.com/review/586-amd-fx-8350-fx-6300/...
Overall the FX-6300 is a decent chip that sits $50 less than the i5 3450 and in gaming will perform just fine. In most games, it's more important to have a good GPU rather than a good CPU.

Only critique is the awful power supply.

CoolMax is a good PSU vendor, in that price range I've never had any problems ( I've bought well over 10 of them for builds. ) The PSU is not a make or break deal though, changing it out for another would be easy and wouldnt go over budget.

I tend to recommend a power supply from a more reputable brand, something like Antec or Corsair. They're also relatively cheap but well made.

http://www.hardwaresecrets.com/article/Coolmax-V-500-Po...

"The Coolmax V-500 is a piece of junk. We could only pull around 330W from it. Above that it burned." - Hardware Secrets

"The Coolmax V-500 is a textbook example of why you should not buy a USD 20 power supply. Its inability of delivering its labeled wattage is not its worst problem. It presents lousy efficiency... its voltages are out of range, and noise and ripple levels are above maximum allowed. A perfect weapon of mass destruction. Stay away. " -Hardware Secrets

Hardware Secrets is one of my most trusted reviewers as they put the tested power supplies through a rigorous test. Even though the system above might not pull that wattage, I'd still like to turn on my computer knowing that it won't explode that day, and take my components with it.

+1 against that PSU. Antec, Corsair, Seasonics, PCP&P are some better investments. sure you can try your luck and hope to get an exceptionally good batch from Coolmax, but not everyone is lucky.

also 2x4GB 1600mhz DDR3 > 1x8gb 1600mhz DDR3, all for a few dollars more