If you are satisfied with what a theme that is available on your Orchard 1 DotNest site (see which themes are available) you can use that as a base and extend it. Just enable the theme you want to build on (Pretty Good Bootstrap Base Theme is a good base theme for example) and also enable the Theme Override module. You can then modify the styling under Theme Override Settings in Themes freely (including CSS, JS and Placement).

You can even override shape templates by enabling the Liquid Markup Templates feature and writing templates in the Liquid Markup language through the built-in Templates module (see the documentation of the Orchard Liquid Markup module on what you can do with it).