I'm on chapter 12 in my NG+ run of Y:LaD, this is where you reach Sotenbori and, more importantly, the battle arena, which is far and away the best place to grind in the game. Purely for money purposes, the management mini-game is the fastest way to get rich in the game, but the battle arena gives out the most exp, you get high-end crafting components, and you make a good chunk of change to boot. Once I get everyone to rank 40 in every job (I won't lie, this will take a while), I can blitz through the rest of the game in a sitting, two tops, and be well prepared for Legend difficulty.
As an aside, one of these days I really need to take the time to learn some of the asian gambling games. There is a metric ****ton of them in all the Yakuza games and I'm completely clueless when it comes to them.