Cable recommendations for my new (preowned) system...

what are you using now?

what’s wrong with what you have now ?     think you are missing something?

thinking you don’t want to spend a lot ?

Interconnects:

I'm a bargain hunter, and I like LOCKING rca connectors, you move something, you may disturb something else..

I bought TWO of these 99.9999 % pure OFC copper Video Component Cables

https://www.ebay.com/itm/122028614401

peeled them apart, ended up with 3 pairs of interconnects, and each pair's locking connector's are a different color. Simply mark both ends of + leg with red tape.

The Cable Company has a used cable site. Most cables are 50%.

Given your equipment I would recommend all copper which would not overly highlight the treble and generally be a little warmer. I would not spend a lot of money… say less than $50 per set. At the cost level if you spend too much the investment would be better spent on component upgrades. As your system changes the resolution increases and the greater the difference interconnects and cables become.

Typically:

copper is warmest
silver coated copper intermediate 
all silver very detailed but will highlight any flaws in components

Speaker Cables: I built my own using OFC Cat 8,

https://www.ebay.com/itm/174307181712

pick your length, pick your color, cut off the connectors, strip the eight strands, put pure copper spade/banana/.... connectors on the ends

I used RED and BLACK, made twisted pairs, taped every 3 ft. Order a bit extra length, twisting shortens them some, cut the lengths after you twist them.

(8 x 22awg equivalent to: 13 awg)

https://www.wirebarn.com/Combined-Wire-Gauge-Calculator_ep_42.html

spades/bananas/ ... : caution: pure copper, it could be pure red copper, you want OFC Copper, typical spec is 99.9999 pure. they will have a thin plated finish so they don't corrode. I use the type with 2 set screws, and they need to accomodate up to 8 awg to make sure your 8 twisted strands fit inside.