Wanting to learn is a good thing.
However, building a decent computer for gaming or any other purpose isn't rocket science. If the components are compatible they usually work as expected and as I've previously said, a regular Joe won't notice minor differences in nominal speeds.
There's a bunch of questions one should answer while planning a new rig: What will be the toughest application to be run? What are the requirements for said application? Are there any known issues with some component running that application? What is your budget? If the answer to the first one is AH3, the second will be a multi core processor higher than 3 GHz plus a midrange to high end video card, the third is being suspicious about AMD processors because some models only can use one core for AH. Your budget is what forces you to make compromises, more or less. For $10,000 you can get a rig that can run anything at max, for $1,000 you can get a good balance between looks and speed, for $500 you'll have to lower your expectations a lot.