What is the most important cable in your system

Lol, it's all subjective....some Here I think fool themselves into hearing a difference, when there is not. Some things in audio are mostly a big waste of money. Yea cables matter, to a point....

Power Cables but your AC Outlets at the Wall are even more important ! 

Quantum Science Audio Ultra Black-Red AC Outlets from Tweek Geek 

 https://www.tweekgeek.com/quantum-science-audio-ultra-black-red-ac-receptacle/

Just thinking out loud:

1. Ethernet 

2. power 

3. Speaker 

4. interconnect 

The cable from the Turntable to the phono preamp.

@sandthemall I agree.

YEP. PREAMP TO AMP THEN FOR ME.POWER CORD TO PREAMP