There´s different schools as well.
One departs from the directions.
The other one totally ignores them, that is to say use them differently. Very confusing.

I bought books long time ago, it is cool actually.
What you basically learn is balance in the use of colours and materials.

Dunno about your budget, but you could hire an expert for one time and compare with your own knowledge.
There´s loads of info on the webbs.