need to learn some theme building

I think the next thing I need to learn is theme building. I know what I want, it's just doing some reading so I can learn to take a basic theme and make it mine.

It frustrates me that I don't know how to change things like font size, background, width and such. Of course, I'll need to figure our how to make a new theme transfer to phone/tablet and still look good. Would say I have to hit the library but, lol, that just shows my age. Micro Center  and Amazon here I come :)