Very difficult achievement. To get a gold medal you will need to meet the requirements for each mission all three times, but there are several very difficult missions which are nearly impossible to get even once. My advice, if you really want to go for this, is to level up your character as much as possible, at least up into the mid-20's. You will still need an insane amount of time and luck to get this though, as some of them are just idiotic (like hitting three smashes in a row, as the bot will almost always be unable to return one smash.
Gamer p3rvypri3st has some videos on his youtube channel showing how to get most of the tricky ones at gold level (he has all missions completed to gold). His character is very highly leveled, but the videos can still be helpful in working out what approach to take.
Channel is here - http://www.youtube.com/user/p3rvypri3st