http://www.teammagma.net/teambuilder/?6,707,94,445,241,658

This is a team I set up, and I need to know if it's any good. I've never tried the metagame before, so any and all criticism is accepted. The team consists of Mega-Charizard Y, Gengar, Miltank, Klefki, Greninja, and Garchomp. I don't care about EV's, IV's, or Natures, I just catch the Pokemon I love, train them, and play for fun. I do care, however, about the abilities, so I will list them here. Gengar has Levitate, Miltank has Scrappy, Klefki has Prankster, Greninja has Protean, Charizard has Blaze, and Garchomp has Sand Veil. The moves that each Pokemon has is as follows. Charizard has Dragon Dance, Earthquake, Solar Beam, and Flame Burst. Gengar has Toxic, Hex, Venoshock, and Trick Room. Garchomp has Rock Tomb, Dragon Claw, Sandstorm, and Aerial Ace. Greninja has Dark Pulse, Ice Beam, Water Shuriken, and U-turn. Miltank has Thunderbolt, Power-Up Punch, Gyro Ball, and Zen Hedbutt. Klefki has Thunder Wave, Play Rough, Switcheroo, and Fairy Lock. The items being held are as follows. Charizard holds Charizardite Y, Gengar holds Black Sludge, Miltank holds Leftovers, Garchomp holds Shell Bell, Klefki holds Sitrus Berry, and Greninja holds Chople Berry. If anyone can give me an honest opinion on whether or not this team is good or bad, I would greatly appreciate it.