Best theme to start off with, when developing it into your custom theme?

OK, so I want to create my own custom built theme, but thinking it might save time if I start out initially with a pre-made theme and then go about changing everything such as the header, sizes, sidebar etc.

I’ve used the Genesis Framework, but that just confused me as it doesn’t work the same as standard themes such as Twenty Eleven.

So what would you say is the best theme to start off with, that will allow me to change the dimensions, columns, header size etc, with ease?