is it true you can get tsukasa and the others as partners (please keep this as less spoiling aas posible)

Yes. You can also get Suberu, Sora, and Helba.~Atari

im still a little bit of a noob so can you tell me how to get new members to my party

You must wait until you meet them in the game. Helba gives you those three's plus herself's member addresses after you beat the game.

To be more specific, you get the e-mail from Helba after you get the book of daybreak from Aura in Bursting Passed Over Aqua Field. (You can bring someone else, but you have to bring Orca)