I would recommend armor as a baseline and then switching to the mega stone if you need extra offense. Leftovers might even be viable in some spots. Also, as soon as you can get a better nature than calm, like impish or careful for defensive ttar or adamant/jolly(more adamant) for offensive ttar. You don’t want to hinder your own attack if you’re gonna run physical moves. You can always be looking to expand your moveset to adapt to certain situations. For example, the elemental fang moves can be retaught to ttar, it can learn stealth rocks, toxic, taunt, and sandstorm as its own status moves to deal passive damage (sandstorm to reset sand or override the weather). Rock polish and power-up punch work as boosting moves for it. There’s a lot of avenues to explore. The gen 6 bulbapedia page on ttar’s moveset can inspire you if nothing here seems to.
Above all just have fun with it and good luck.