So u don't think the game is boring. Because the goals are the game: Beat Arcade mode, Combat Trials, Play Versus, online, with friends, Get wins, kills, belts. So if the goals are boring the game itself is boring.
What I'm going to do is just keep playing online for a long time and then see which ones I have gotten in that time. U don't really need to think about them all that hard doing it that way. Plus they also help u rank up your characters.