I'm looking to get into SMK time trialing, so I was wondering what format I should play the game in. Wii VC is the easiest for me because I don't have a ton of money to spend on an official cartridge, and furthermore I don't have an official SNES, only a Retro-Duo, so I don't know how it's controllers would impact this. (Though I do believe it supports official controllers so I could look into that) Any advice?

You must play Super Mario Kart using a real Super Nintendo (not an emulator) or the original Wii (not Wii-U!) Virtual Console version, and be playing on Time Trial Mode. Super Mario Kart was also released at the end of March 2014 on the Wii-U in NTSC format, however you are NOT allowed to send Super Mario Kart times raced on Wii U Virtual Console because it has a save state feature, giving it an advantage like an emulator. All of your Time Trial records will be required (20 tracks, each with 5-lap and 1-lap = 40 times) for you to be listed on the rankings.