Thank you everyone! I ended up just setting the ruby in the argentium ring and will probably keep it silver. The next ring I make I will use as a trial for gold plating over argentium. I do intend to wear the ring after it has been plated in order to test its durability. Hopefully a thick enough layer might hold up to typical wear, although I will have to trust the person plating it as far as how many microns actually end up being plated onto the metal.
I love the look of gold but find that gold-filled is just too difficult to use in pieces that call for multiple solder joins as well as exposed core metal. The pieces I'm making right now are for myself so, alas, are not worth spending the money on karat gold.
Thank you for your expert feedback!