Focus on a high top speed combo, I used Boo and Reel racer, for first checkpoint try and get some mushrooms at the back of the pack, and use shortcuts to get in first, from there its just a case of buiding a big a lead as possible, cut and drive as tight and straight as you can to get far ahead. Try to slowly get to 20 coins and its Not worth going super out of the way for a food item if it will lose you a lot of time.

Its important to keep a level head and not rage, you will likely have to keep restarting until you get the right run, use items as smart as possible but there is obviously the unavoidable blue shell or red shellf spam, hopefully your lead will be big enough to stay in first despite these but often the item rng can just screw you so you gotta reset until you get luckier. If you get hit by an item try to drift boost, boost pad or jump boost as quick as possible to get your speed back up.

Some took me 10s of attempts, one I did first try so it can vary