Alright so here's how to win a bunch of chips in the casino in Ni No Kuni:

You might want to buy or win 5-10k or more chips before starting this.

I noticed tha tthe slow-down power-ups you can get in roulette stack, so what you want is to slow down the wheels X3. You can do this by using a combination of Lvl1 and Lvl2 slow downs items. Once you have slowed the wheels down x3 its pretty easy to line up 777 on the bottom row.

Doing so gives you a x100 payout on a 90 chip bet max and if you are in mega mode you can multiply all that by two. So a nice 18k chips right there... and you can do it two or three times in a row pretty easily.

To get into mega mode you have to fill up the seven flames at the top of the machine (over the prize payout list) and then line up and 8th one to activate it.

So if you have a X2 and X1 slow-down power-ups lined up you can wait till you get some flames (by lining up icons or using a flame power-up) and rack up the chips.

It can take a while to get a win since it is luck-based but if you have enough chips to start with, you are pretty much a guaranteed win eventually. The chests seem to randomly appear and give random power-ups so this can go pretty fast but you can expect to spend over half an hour to get a decent payout.

Just bet 10 chips until you have the required power-ups and raise your bet to 90 when you are in mega mode.

Update:

Or you could just play Platoon. Following @uniform 's tip, the dealer always seems to play her number cards on the right and her figure cards (king/bishop/wizard) on the left. So winning 6-7 games in a row is pretty easy. I made over one million chips by doing that once, by winning my prediction every round. So then you can trade in you chips for Medals of Agility and sell those for mad Gs.

In my opinion, Platoon is the best way to win chips. I netted 200k chips from beating 6 games in a row.

Platoon is definitely the way to get chips. Playing the other ones just for fun is the better option. It also helps that I find Platoon to be the most entertaining thing in the Casino. Super easy to win with the common strat. Knowing she always places number cards to the right, and Kings/Aces/Jokers to the left. It's basically cheating.

The AI for platoon is crazy stupid. I find in every game she puts a single low level card by itself. I only played for 20 minutes last night and racked up over 200,000 chips.

@uniform: Platoon looked like too much of a risk to me, wagering all those chips and then losing because the AI put a wizard on hits biggest stack of cards and you used a low score wizard to try and steal it... slots is mindless, i was playing it while watching a movie and only paying attention to watch for the power-ups and when its time to use them.

But I will give Platoon another shot when i need more items from the casino. if it really always puts its cards in the same order, it would minimize the risk a lot. And by risk I mean wasted time.

@Swaboo:

But I will give Platoon another shot when i need more items from the casino. if it really always puts its cards in the same order, it would minimize the risk a lot. And by risk I mean wasted time.

Platoon is the way to go for quick chips. If you're worrying about losing money, just buy 1k worth of chips, bank whenever you win 3 in a row, and you will have enough to keep playing until you win 6 games in a row or more.

The casino girls are super cute though. Wasn't expecting that.

That Platoon walkthrough was super helpful. I was losing as many games as I was winning. Thanks fo rthe tips, folks.

They let a little boy gamble in this game?

@Hunter5024: The dead don't care.