So i decided to make a solution just to expand on CDWhildings solution above
So the objective is to find a clown carnival room with the dagger game. So before you attempt this achievement, you should be pretty familiar with the game enough to explore the first castle area without any upgrades etc.
So start a new file and explore the castle until fully explored - If you don't find a dagger game room, delete your save and start a new one. Keep doing this until you have the carnival game spawn.
Now you can take part in the game and hit the targets, but do NOT throw the last dagger. As long as you don't throw the last dagger, you can play the game as much as you want.
Now follow these steps carefully:
1. Throw all daggers except one - generating approx 200 gold +
2. With 1 dagger left, press start to pause, then press y, then quit to main menu. This will make what i will call a soft save. It will bring you back to the press A to begin screen. You can then press A, and you will start at the start of the castle with the gold you just acquired. Now make your way back to the dagger room and repeat.
3. Do this as many times as you want until you have had enough.
4. Now you need to do a hard save. Repeat the steps for a soft save, but when at the press A to begin screen, press the guide button, highlight the game and press start, then quit the game.
5. You should be back on the dashboard - this will then hard save your game to the cloud system. Make sure you do this every time you have finished grinding, or every 5-10 k gold to be safe.
WARNING : DO NOT FORGET TO QUIT THE GAME. IF YOU START ANOTHER GAME OR JUST TURN THE XBOX OFF INSTEAD YOU MIGHT LOSE YOUR PROGRESS.
6. Repeat until you have enough gold that you want.
Just be careful you do not die when heading to the carnival room every time. There are 3 barrels that can give you hp, but do not die or you will lose the castle and it will be randomized again.
Hope this helps someone.