Dolphin, the GameCube and Wii emulator - Forums

If you only do a mild OC like 4.2-4.3GHz (Vcore < 1.3V) , you won't need aftermarket cooler . Just stock Intel cooler and Arctic MX-4 will work
At 4.0GHz , most games can reach full speed already ...
In the past , the only game that need heavy OC was The Last Story . Nowadays , just use Directx 12 back end and then even 3.4GHz Haswell can run it full speed

I would not buy a G3258 anymore. It used to be super popular but things are changing fast and I've seen people recommending against it now. Skylake is also great for emulation, seeing a 10-20% boost from what I've read. I recommend the newest i3.

But honestly, I have the newest i5 in my rig, the 6600K, and no graphics card. Still, I'm getting 60fps in all Dolphin games I've tried at 1080p. So, if cost is a problem, maybe you can build a pc with no graphics card at the moment, and get a graphics card later. Because the integrated graphics of newer chips is really really good. I can get like 30fps with Alien:Isolation on ULTRA with the integrated graphics of the 6600K.