yeah, if your composing or playing something in the key of C you would focus on the Dominant which would be G and the third which would be E. When composing a bassline of some sort it makes sense to pretty much make these notes the focus. There is definitely more you have to know in order to make a proper line though and thats pretty much where progressions come into play.
this is a great site to learn the basics of theory. The school I go to is always recommending it to the incoming freshman. And its pretty much all you need to know in order to be a producer, imo.
That helped a lot with a thing or two I didnt know.thanks man.