Her is a deck strategy I have though of. It is based on Mega Mewtwo EX. I have not made this deck because I do not have enough cards to.
Here The Pokèmon you should use.
It does not matter is the card you use looks different as long as it does the same things.
The deck's strategy is to make M Mewtwo EX to do as much damage as possible by attaching energy to it. I choose the Mewtwo EX used in this deck because has an attack that does more damage the more energy attached to it like M Mewtwo EX. Garbodor is used because of its Garbotoxion Ability. It stops Pokèmon that have ability's that make M Mewtwo EX unable to attack. I would put in 2 or 3 but you can use as many as you like. Which Garbodor you use should not make difference because you do not want to go into battle with it. You should only put in 1 Trubbish so that you do not start with it instead of Mewtwo EX
You need lots of Energy. Maybe 30 Psychic and 4 Double Colourless.
It does not really matter what trainers you use but some good chooses are down below.