Help making/re purposing a theme.

Okay, I really like thesis. The thing is, right now my budget is going completely towards advertising.

How can I start making a theme like that? Please make it simple, language a mediocre tech-saavy guy could understand. THesis is the theme being used on https://newmoonmovie.org, by the way. I like the fonts (what is the font name?) and the design with the header outside of the main body.