I gave my son my old computer and wanted the least expensive option to be able to play most games and have a responsive system. I thought about using an old case from an eMachine, but decided to go with a microATX.
Case: I read a couple of bad reviews about this case, so I was prepared to have to buy a new power supply. I was comfortable with 300w for this build, but worried that it would be DOA or fluctuate too much. I have been using it for a couple weeks now and it seems fine. Some reviews mentioned the loud fans. It comes with two 60mm fans on the back. They are louder than I would like, but not as bad as some have mentioned. Note: You may read that this case has room for a 120mm case fan, but it does not. It has a spot on the side of the case where an 80mm fan could go and another 80mm space at the front bottom, below the 5.25 slot. If you have any sort of heat sink, though, the side location is not an option. The only other thing to mention is the cutout where the front panel wiring comes through. It is hard to tell from the picture, but it is a little sharp. I thought that it may eventually cut through the wire casings, so I lined it with some electrical tape. Oh yeah, one more thing. The slot for a 3.5 drive under the 5.25 backs right up to the cpu cooler. I did not have room to plug in the power and the hole configuration did not allow me to move it up. I decided to put the drive in the side slot.
Motherboard: I was able to get a $10 rebate on the board. It fit perfectly and has and IDE port and built in VGA. I thought that I would put off getting a graphics card and use the on board video for a while. I has ATI HD 3000 integrated graphics. They were good, but could not run newer games. So, I ended up getting a card sooner, than later. This board has plenty of SATA ports and also built in IDE, which was nice. I may put another old drive in.
Memory: Nothing special. Works well and was the cheapest that I could find at the time.
Storage: I wanted to get a 1 TB drive so I could dual boot with Ubuntu and Windows and still have enough room for both. Again, this was the cheapest good drive I found.
Graphics card. I got the R7 250 from Rakuten and saved $30 by signing up for a credit card. I decided to get this over the GT 640, which was my first budget choice. This seemed to have better reviews. I am happy with it. It plays PlanetSide II well, which was a benchmark test, since the computer I gave my son could not run it.
Optical drive: I just went with a cheap DVD writer. Did not need anything more. I had an old IDE DVD writer - I could have saved some money here and just used that. But, I had already ordered this, when I was originally planning on a different motherboard that did not have IDE. It was too much money to send it back, and it works well.
CPU: I went with the AMD cpu to save money and still have a fast system. Originally looked at the quad core, but seemed like a good deal for a few dollars more to get a 6. From what I have read, it will not make much difference for most uses, but it still feels good to have 6 over 4.
Monitor: Read a lot of reviews that said to get IPS, but again, looking for a budget system, they were a little too pricey. I wanted something 21"" or more and found this Acer on sale at Amazon for $99. I had some Amazon points from using a Chase credit card, which brought it down some more. I like this monitor, it is bright and crisp and responsive. the down side is that it has no height adjustment.
My budget was to be close to $400. Originally, I intended to reuse an old case, and old IDE hard drive and old DVD writer. I got carried away and bought all new of these, but still came in at under $450. I may get a quieter fan yet, but that is just $10 or so.