If you are going to build a PC for gaming, what is your budget?
One of the biggest expenses on any gamming PC build is your video card. This also depends on what resolution you are gong to be gaming at
I.E.
My monitor is 2560x1440 which is demanding on a video card which is why I went with a top end card
If you are running less resolution you could get away with less
Basic Tips:
1. Determine your budget: Lower end gaming rig is around $600 to a higher end which can reach about 3K
2. Determine your monitor and resolution
3. Very highly recommend getting an SSD drive for OS, huge difference in boot up time and gaming
4. If you are planning to Overclock, then invest in a solid aftermarket cooler for the CPU
5. If it's in your budget, I strongly recommend a modular power supply (where you only plug in the cables you need) makes the build so much cleaner
6. You really don't need an aftermarket sound card because there are really strong ones for gaming on most motherboards
7. I have build PCs with ASUS / EVGA / MSI / GIGABYTE motherboards and have noticed minimal difference between all, though I would stay away from VGA
Pick Parts, Build Your PC, Compare and Share - PCPartPicker
This link will help you to get an idea of components to build a PC. It is extremely easy to do, as long as you can read and know how to plug things in, its really simple. Just make sure to follow instructions. Motherboards of today are pretty much idiot proof.
I could go on for a long time, but really determine you budget and find PC Parts stores that are in Australia because I have no idea.