Inexpensive speaker cables

Oxygen-free copper, as large as your connects can handle.
I remember reading an analysis by a materials chemist who looked into the subject.  Anything else actually degraded electron flow, which would allow for the subjective differences noted by listeners.  The upshot being your cables acting as a subtle equalizer...if that's what you want....
Always seemed like an expensive way to go about it, but to each his/her own.  Enjoy...

a fairly large dia. for speaker cables, yes - but be sure the conductor is large; some cheapo cables have very fat plastic insulation and thin wires!!

most cables are "Oxygen-free copper" except maybe the cheap imports and... if they say Oxygen-free copper how do you know it really is

Belden is a quality name for all wiring

also, there are some liquids containing conductive polymers that you can use to coat the connectors; I have a tiny bottles form many years ago, and I think it might even be called Tweek ;]

that will help reduce corrosion at the connection

the wires that have served me well are, for biwirng : "soft sounding" canare 4s11, and for single-wring, the fairly neutral belden 5t00up10awg, and my favorite for its superior neutrality, definition, control, lightness, and flexibility: the canare 4s8 13awg.
These can be had for relatively little cash.  Add techflex and they can look really good.

best speaker cable available in my opinion in Mogami 3103, 12 gauge but closer to 11awg
very flexible
cant go wrong