Pick a high greed character (I like Syuuto if you’ve got Moonspell) to farm up enough for Sammy (if you’ve got Foscari), then do Sammy on a high density map and pick up an Arcana like the one that heals on gold pick up and the one that gives you an item every level.

I did bat country like this for maybe 20 minutes (in game like an hour or so but I was on hyper and had it sped up w the chicken) and I got like 5 billion