So, I have a decent idea of everything to do. I know all the parts i need, but im not sure how you know, what MB etc will fit into what case? I'm planning to build a good gaming PC bf3 high standard Don't worry about budget, im on mid-range sort of a budget. So is AMD MB better for gaming? Nvidia vc? I'm pretty much a noob at this so some suggestions would be nice, Where do i start?
The best place to start is by providing more information with which people can help you. There is a template in the Systems forum designed for asking about builds, it might be a good idea to look at that and provide more information.
One thing to mention would be that budget is always important, whether you have $500 or $5000 to spend, and while you mention BF3, you don't mention what kind of detail or resolution you want to be playing it, it has a huge bearing on cost.