Mario Kart 8 Deluxe: 12 Tips & Tricks The Game Doesn't Tell You
4. How To 'Finish The Game' & Unlock Gold Mario
Weirdly, Mario Kart 8 doesn't show any sense of progression or list of goals/things to accomplish. Outside of telling you of more kart customisation items being unlocked as and when you get them, 99% of characters are unlocked from the get-go, as are all the courses.
To that end, MK8 is ostensibly best enjoyed through the competition of playing online or with friends, but if you're looking for some set of requirements that'll allow you to say you 'finished it', there are two specific things to keep track of.
First, get bronze, silver or gold trophies in all of the Cups within a specific speed class. This will get you the final credits cutscene, and some sense of finality to your efforts. And second, get all gold trophies within the 200cc class, to unlock Gold Mario.
He's more a glorified drivable trophy than anything else, but at least Nintendo included a way for players to show off that they've mastered the offline single-player.