I hoard every single drop of trinity crystals to fight the gatcha beast. At level 60 you get a daily mission to spend 300 stamina in the secret realm to get 2 rainbow keys: I can hit that without using crystals to buy stamina, and my burger reserve is still steadily increasing.
As for red ore I gamble for ssr weapons 3 times a week: its truly a gamble, as there lots of junk ssr weapons and fewer junk armors and helms; but a good ssr weapon can be game changing.
Mithril ore is only good for scrolls and gold later on, but I would suggest gambling for sr helms if you dont have a sage hat. There are also lots of good sr helms that has the same effect as their ssr counterparts (horror helm, performers mask)