When you get to this point you'll have already cleared 6 completions of the game to get the achievements for each of the 6 characters.
You'll also have earned coins while you got the achievements for completing the game without a 'retry' or 'continue' and the achievement for earning all three stars in each level.
This will get you to around 70,000 coins.
To get your remaining amount play through the levels again until you complete 4-3 to power yourself up as much as possible.
Then instead of playing level 4-4. Return to Level 1-3 and play. The achievement tracker for this achievement only counts the coins once the level is complete, so collect as many coins as you safely can, and you'll be able to pick up roughly 3000 coins every 6-7 minutes.