It's no surprise that the first (and hopefully not only) DLC/update to Super Mario Odyssey contained three new outfits and Luigi's Balloon World mini-game. This is a quick and fun way to score a LOT of coins, and in my opinion far better than the Cloud Level exploit in Bowser's Kingdom...
It consists of two modes. Hide It, and Find It, both of which are self explanatory. Hide It has you hide your balloon anywhere you want in that Kingdom's overworld, so no mini-game or boss areas are allowed. You will have 30 seconds to hide it, and the longer you take, then the longer other people will have to find it if they choose your balloon in Find It mode. Collecting coins will add 1 second for every 3 you collect. This can help you get balloons further if you wish.
Find It is where you choose a balloon of someone and attempt to pop it by either touching it or hitting it with Cappy.
Whichever mode you play, you earn coins, and the more you play, the higher your rank becomes, and the higher your rank, then the more coins you earn just by playing. If you want a lot of coins quickly but wanna have fun doing it, definitely do this.
9/10 - I do wish you had more time to hide balloons and that you weren't restricted so much, but still an addicting little time waster.