Good question :) I was looking into a budget build and I would recommend either the AMD or Intel budget build guide which should be on the completed builds. I used the AMD build as a template and built it up. This computer runs rainbow easily over 60fps on high settings and the limiting factor for performance is my internet.
Try going through the completed builds and taking one you like and was used for the same things you want, that may help
Thanks, do you know if it would be worth downgrading the graphics card in order to get a wireless network adapter? Also, would it be more advisable to have a single 8GB of RAM instead of 2x4GB or does that not affect it?