However you can never sound original and will be very limited if you stick to the scale with diatonic chords only e.g. 2-5-1
The typical theory tends to break down when trying to explain chords outside the scale non-diatonic.
Here is a simple Colour / Numbering method with shows you how to construct non-diatonic / interesting sounding chord progressions.

https://soulful-keys.com/chord-system/