So I want to start running super monkey ball 2 but I don't want to shell out 80-100 bucks for the disc then another 100 for a decent capture card. I have the dolphin emulator of the game, would that be acceptable for use on that game? it says that you can only use the original disc but there's a logged run on an emulator. so can I use it or not, and if I do use it, can I submit it. and one last thing, if you're not allowed to then why?

That question would be best asked on the game's forums: https://www.speedrun.com/supermonkeyball2/forum

What ROMaster said.

But if you want a general answer, the reason Dolphin most likely isn't allowed is that it's emulation is probably faster than the Gamecube itself.

Also, if you're US located, it doesn't cost nearly that much to run this game. There are tons of used copies out there for under $20 and a gvusb2 capture card (arguably the best standard def cap card) is only $30 to $40. You don't have to spend nearly as much as you think to run this game.