...I beat the K route and even fought a ton of enemies I hadn' seen yet (including The O!), but only unlocked 00 Raiser. This game has sooo much to offer, it's even bigger than the jump between Fed vs Zaft and Fed vs Zaft II+
Not to insult anyone's intelligence, but the difficulty is on 4 by default. If you haven't played before, you can set it easier to get a feel for the game first. I only say this because my friend was all pissed at the first GvG and I realized he didn't know the difficulty was so high.
edit: Page 7 of the in-game manual, why does it have Gym?! Is he that excited about getting points?