You must have 69 coins at the end of the run. This includes the Slots at the end!
You will want to slowly collect coins, avoiding the larger clusters as you approach 69 coins. Try to grab just the last few coins out of a line until you hit 69, then kill yourself. If you have accidently picked up a slot token, you will want to gamble it instead of cashing it in. With any luck you will not get one of the coin rewards.
Alternatively, you can collect 19 coins and 1 slot token. Cash in the slot token for 50 coins to reach 69 coins.
Finally, you can purchase and equip the Flying Pig, which randomly appears and drops single coins. Collect 63+ coins and then wait for the Pig to appear, collect the coins until 69 then dodge the pig. Once it has disappeared, kill yourself and the achievement should pop.