I only have around 3k zeni now. Initially I was spending it on the daily shop to get Hero Memories, but now I realize it's not worth it. Zeni is comparatively more limited since you only get it from the season pass, while you get Hero Memories from playing the game. You have to use more Zeni than Hero Memories to level up a character too, so never spend Zeni on Hero Memories, it's worse in the long run, even if the "cheap" prices in the daily shop look appealing.

This is annoying, I feel that if you have Daimaku, you can have 12 characters without worrying too much about the grind, but once you have to make characters level 3 and beyond... With the amout of Zeni I have now, it won't be enough (Since I have to level up Dabura one more time), so I'll have to get a little more zeni for the next character at level 31, but from then on it'll be a pain in the ass.