A great all round team would have to be
Charizard: Fire type can inflict huge damage upon grass types which are most commonly encountered, this may also have an after effect on the opponent, burn.
Torterra: Covers variety of pokemon with leaf storm, giga drain and crunch very effective when encounterig rock type pokemon.
Staraptor: A nice addition to the party, with really effective moves such as aerial ace and brave bird.
Giratina: A good pokemon to be used as a distraction to bring out another pokemon with a large supply of HP. And good moves such as dragon claw and earth power.
Electivire: With plenty of HP and some powerful moves this is a good electric type to choose. Move like thunderbolt will almost paralyz the opponent every time. And its giga impact can Ko a pokemon in one attack making this a great addition to your party.
Blastoise: Is a fairly reasonable water type to have, With the heavy hydro pump it can do some serious damage.