Here’s how you can use the Responsive Grid System to suit your content:
The ‘Intro Page’
Has a header row with a logo and some nav, some featured content (maybe a carousel or some headline text), a row for the smaller features and a footer.
Has a header row, a row with the content and the sidebar and a footer.
Has a header row with a logo and some nav, a couple of rows of portfolio items and a footer.
The ‘Golden Ratio’
According to wikipedia, two quantities are in the golden ratio if the ratio of the sum of the quantities to the larger quantity is equal to the ratio of the larger quantity to the smaller one. It has a value of 1.618. If you use a grid of eight, and split into five columns and three columns the ratio is 1.66, which is pretty close.