I came close to winning with my Rain Dance team. Friggin Milotic was no use to me, though. Kept dying before I could set anything up.
The GS kept changing the rules, too. First they claimed that you could use one legendary, then before the first match starts, they say no legendaries, so people have to re-arrange their teams. Then they start round 1 with a single battle, and then the next with a double battle, claiming that all matches are default double unless both consent to singles. Very frustrating.
One thing I found out about my team, however, is that it works wonders in doubles. I even kinda "cheated" in my second round match by claiming I wanted to do doubles against a guy who I KNOW would've kicked me out in a singles match. But even with things like that, I could do nothing against a Blissey.
One of my friends went all the way, though, with the Ninjask/Marowak combo, and nearly won, but lost against the guy who beat me (he also won the whole thing). Still, good times.
EDIT: DarknessBear, I asume you have the egg that was just given to you. It's the baby form of Chansey, and it won't hatch for a few thousand steps. Better to wait until you get a Slugma or a Magmar, since their abilities (flame armor/magma body) cut the number of steps required to hatch an egg in half.