How to purchase Rixty:
1) Activate your card
2) Go to the store and buy pre-loaded cards (Wal-mart, Kroger brand stores, 7-Eleven sell them). You can't buy Rixty online with a wells fargo visa gift card because the transaction comes from Ireland and out-of-US purchases are not allowed. BUT because the store is the one who pays Rixty for the cards, using your credit-card in store to buy rixty works because you're paying back the store. Confusing. But it works! I did it.
3) Cash them in on the Rixty site.
How to purchase Rift Credits
This is trickier because if you activate your card online, you can buy rift credits, but just not so much that it completely unloads the card. There is a way around this. You buy Rixty money as above and cash it in to buy credits.
I started off explaining the process it took me to learn all of this, but really, it's just a bunch of bureaucratic poo. In short, I did file a ticket with Trion to let them know about not being able to completely unload the card directly through them, and how crappy that was because I've been able to completely unload cards for Riot points.