The gameplay in Mario Party: The Top 100 is centered around competing in various mini-games, including Minigame Island, where players can unlock new minigames by progressing through the map, and Championship Battles, which pits players against each other in a series of three or five minigames. There's also Decathlon, a test of overall skill in five or ten specific minigames, and Collection, where players can view their wins and unlocked content.