Best spots for grinding Gacha tickets?

Now that I'm unemployed, I have a lot of time to do what I love most - grinding for Gachapon tickets.

To do it, I created a new Ice Mage character so I can comfortably and quickly grind in places and kill monsters as fast as possible to get gacha tickets.

Right now, I'm grinding at the Bubblings, but it feels like the drop rate of the tickets is about the same as if I were using a character like a Cleric, for example (I should note that the number of monsters I'm killing right now is at least 4 times higher).

It might balance out in the future, but anyway, I wanted to ask if you know of any other places with a high spawn rate of monsters where I can grind, with one-shot kills? I'm not looking to level up or develop the character beyond that.

Additionally, if you have any other tips around this, I would love to hear them.
I really love Gachapon.

Thanks!