I'm starting placement matches and I played one till now, I lost it, what do they look at when deciding the rank, the unrated games or the kda, can someone help me?

Hello guys, me and my friend are new to the game, we started playing 2 days ago. I see everyone using weapon VANDAL, but there is also another AR called PHANTOM. Is Phantom like, really really bad? Can we use it, or it's waste of ti...