Thoughts on how this budget build would work?

That power supply is terrible. It could literally blow up your PC or burn down your house. At that price point, it makes more sense to pirate Windows or just use the free version (you won't be able to change your desktop background and it will have a watermark on it but other than that it's the same as the paid version) so you can put your entire budget into the PC itself. You should get something like this instead: http://pcpartpicker.com/list/HnzGnn

It's not bad.
The G3260 is a bit faster and cheaper than the G3258 if you don't overclock. The G3258 is better for overclocking.

You might look into trying an 1151 socket system rather than 1150 so you have faster CPUs to upgrade to. You can still get Pentium CPUs for the 1151 socket.

The G4520 gets about the same per-core performance as the i3-6100 mentioned by the other guy, though it's slower at multi-core stuff.
http://www.cpu-world.com/Compare/294/Intel_Core_i3_i3-6100_vs_Intel_Pentium_Dual-Core_G4520.html

The G4500 is the same price as the G3258 and is quite a bit faster.
http://www.cpu-world.com/Compare/190/Intel_Pentium_Dual-Core_G3258_vs_Intel_Pentium_Dual-Core_G4500.html

Let's go with this instead: http://pcpartpicker.com/list/WmxNgL

We'll hope the prices go down a bit during Black Friday to make up for the +$30, you really need an i3 as a minimum, at a performance stand-point I think you would regret that decision if you got a Pentium or Celeron.

Some observations:

1. The Intel Pentium G3258 you had is old, no reason to buy that
2. Motherboard that went with old CPU is old too
3. RAM that goes with motherboard is also old
4. I think you might as well get an SSD for this price
5. This eVGA PSU is not great but much better than COOLMAX (poor choice) and is on super sale so way cheaper

Another consideration would be the Corsair 88R case I think. Smaller cases can be a pain to work with in my experience.

Looks like a decent low budget gaming build, but if your going with such a low amount on disk space why not get an ssd as it would be much faster boot time & game performance.