My only advice would be to check your portions. They regularly miss ingredients or only half-fill tacos. Pretty forthcoming with crediting your account but that's only helpful for your next visit.
It is a f2p and there is a cash shop, but it is tiny. And I haven't bought anything from it, and haven't felt the need to. The progression plays like a normal game that has quests, and it isn't really p2w either. You can earn all currencies by just playing.
I have unlocked depth 3, but didn't get to the boss. I got popped by some abomination two nodes in haha! I've been leveling up the frost mage and the assassin lady to try and get further. I can't decide who I like more, or whether I should unlock more characters, I have plenty of gold.
Edit: I actually cannot stop playing, this is a really good game! I like the story too, it makes it feel grounded. Thank you for mentioning it on the dt Gibs