Inexpensive speaker cables

OP, what length are you looking for?

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.