I recently started working in a Deli and decided to see what kind of a machine I could build on deli clerk pay. I managed to keep costs below $300 using some low cost, high performance (relatively) gear and some used parts.
The G3258 is overclocked to 4GHz right now, but I'm sure I'm can get it higher. It is a low TPD CPU, so the Cooler Master T2 should be adequate for any overclocking I might do.
The MSI H97 motherboard was used from Ebay and has worked flawlessly.
I put a used PS in originally, but it just didn't have the oomph I needed, so I upgraded to an EVGA 500W from Newegg.
The Xion case is small, but cheap and has been just fine for my needs.
The Klevv Fit RAM overclocked without any problems and was a bargain.
I was originally using the G3258 internal GPU, but upgraded to a used EVGA 550 ti from Ebay and have been happy with the results. I'm getting around 85 fps on WoW at Ultra settings, I used the NVIDIA GeForce Experience app to optimize the settings and love the results.
For less than $300, I am very happy with the results.