Haha, yeah you should definitely get a Ralts ASAP. They're so useful throughout the entire game. It doesn't start to become worthless like some Pokemon do, some can become weak by the time you reach the Elite Four because they have no more moves to learn, and everyone they fight is better than them. Not Ralts though! I've used Ralts all the way through Emerald back in 2005, and now that I re-purchased a Pokemon Emerald, I'm already training it up. I'm actually surprised how quickly I caught it this time. It was one of the first Pokemon I encountered, and the chance of finding one is "Rare" according to the Pokemon Wikia. It can only be found on Route 102.