This is in no way a full list of stuff to have in mind when buying parts for your first pc. Use it in conjunction with something else. I just wrote down everything thats came to mind that good to take into consideration. Use it at you own risk. There is most likely a lot of errors in it. Actually, if you find something thats correct it must be because someone else has rectifyed it and told me.

Chassis

PSU

CPU

Mainboard

RAM

Hard drive and Optical drive

Graphics card

Operating System