Super Lucky's Tale

This should be the last achievement you’ll unlock. Luckily your coins carry over from your main game, so you may already have at least or near 15,000. Remember to keep in mind when playing through the game to collect as many coins and diamonds as possible as this all adds up.

It’s also worth noting that the coins do not need to be collected within the DLC levels. So the best and fasted method is to load up the Spookington world map and grab the 2 diamonds which are at the end of the boardwalk. One is behind the wooden wall behind the 'Carnival Court' level, then jump on the spring to the right to grab the second one. Now wait for all the coins to be added to your total, now reload the map and repeat.

This method will net you 103 coins (2 diamonds and 3 coins) every 20 seconds and you should be averaging about 17,000 coins per hour. So it should take you roughly 4-5 hours to get the full 99,999 depending on your starting coin total.