Interesting...

https://forums.elderscrollsonline.com/en/discussion/542533/eso-players-mostly-apathy-robots#latest

You posted that at 4:44am my time. This post here, was at 5:44am my time. An hour later. Ah well! Glad to see you decided to keep playing!!!

Honestly, what I would do, is check prices at different guild traders and see how much people are selling the rubedite/tempering alloy for to other players. And if that number is much, much, higher than the price of selling it to an NPC merchant, than I'd join a trading guild. You'll meet alot of amazing people in trading guilds, all while making a nice profit off your materials!! It's a win/win situation!

But if the NPC merchant buys them for more than players sell them for, you could just keep selling them to whichever one you prefer.

As far as a good location to "WTS" goes, since rubedite/tempering alloy is more of an "end game" materials, I'd try to sell it to those in higher leveled content. Maybe in craglorn, or in some of the bought chapters. Like elsweyr or greymoor if you own them? Or, you could just port to any of the big city's wayshrines and try there? If no one bites on your offer, try the next big city. Either way, check prices at guild traders first so you have a better idea on how much to sell them in zone chat for.

Hope this helps!

Dude, get Minion (it manages addons), search and install addons via Minion. Search for TTC addon.

Minion auto updates installed addons once there's a newer version.

And by the way, get into some more guilds - they don't need to be trading in order to you to sell your stuff to others.