I want to add something to atheistium's and Button Masher's solutions. The GOLD, SILVER and BRONZE stars are stackable!
I made BRONZE star using above method, then I quit the VS Match (don't go into Xbox Live yet!).
Then I made SILVER star (using the same method) and quit.
Then I made GOLD (if those were not stackable, I could get the biggest one, you know)... and quit.
Log into DOA Online, find a match and watch it (or fight it). In the end of one only match you can get all 3 stars for the price of ONE Xbox Live match!