We certainly have enough Ralts line. We have a standard one, one going into Gallade and one going for Mega Gardevoir.

Also I think having one Mega Stone at the start is okay. In the games you may be able to use it whenever you want, but it is described in-game as requiring a deep bond with the Pokemon that is mega-evolving. For purposes of the game your player character is an amazing son-bitch who gets along with any and every Pokemon they catch. So not anyone can just simply use it.