
First, take a look at Customize the Ribbon - It Doesn't Take Rocket Science by Greg Maxey. To have a Ribbon Customization that is truly portable, you want to do it by XML modification.
To customize the styles shown you can use the [Manage Styles options]. You can also use [Quick] Style Sets.
You can add elements from the default Home Tab by choosing, instead of Commands, go directly to the Ribbon elements.
Again, though, I urge you to read Greg's page and do your customization in a custom template using XML. It is a bit of effort but well worth it.