Yakuza 4 Remastered

The earliest you can earn this achievement is in Part 3 which is when you first start playing as Tanimura.

I found the easiest way was to buy 1000 chips (requires 100k yen) and gamble them at the casino on Roulette, using the Zero Jewel cheat item (press Y to use cheat items) and betting 500 on "0" and 500 on "00". This guarantees that you will earn 18,000 chips with no risk of losing money or having to reload.

You can acquire the Zero Jewel cheat item in two ways:

-Inside Kotobuki Drugs on a shelf you will find Locker Key C5. Inside the locker (found near Millenium Tower) you will receive the item.
-During the Finale Kiryu has a substory called "Kiryu the Babysitter" which awards a Zero Jewel on completion.

There are two casinos - one in Dragon Palace (unlocked as Tanimura in Part 3: Chapter 1 upon completion of the "Gambler's Blues" substory) and one in Purgatory which Tanimura can't access until the Finale.

I personally did Dragon Palace with the Kotobuki Drugs locker key Zero Jewel as it's the fastest way to knock it out.

NOTE: If you've claimed the Zero Jewel as another character by finding the key and opening the locker while playing as them, you'll need to wait until the Finale to transfer the item as your inventory between characters is not shared until then.

In the event that you've already used both Zero Jewels, in the grand scheme of things 3000 points isn't too hard to come by - especially given that there are several other (weaker) cheat items for the different Casino games all of which can help with the achievement.

The 18,000 you earn from this can also help towards the Walking Bank achievement (possessing 10,000,000 yen). You can even bet 1000 on 0 or 00 rather than splitting for a payout of 36,000 chips, but it may require reloading the game if it lands on the wrong one.