I cant count how many times I've tried to get a gold in either one and I can't beat it, no matter which character or gear I use. Unless there's a specific character or gear I should use, I'm about to give up at this point.
Hey don't give up. I suck at this game on the beginning but I learned all you have to do is keep playing all stages and learn all the shortcuts for each type and eventually you'll be laughing at how easily you become first even if you get a bad start. I already won most of the gold emblems, I'm working on Sega Carnival/Illusion then after that I'll just finish the extra missions then I'll finally get my chaos emerald for the supersonic character!
Mission mode actually helps a lot, it took me so many tries to get gold on the Heroes Cup (I didn't do any missions and just practiced on free race mode). After I did the missions for the first four Babylon tracks, I knew every shortcut and got gold in the Babylon Cup first try.