A Flareon GX deck that I've built.
It's whole theory is to put pressure onto the opponent very early on to try and quickly win the game.
You want to get Flareon GX out onto the field as fast as possible. Sylveon V can search out Professors' letter to place energy into your hand or Pokemon Comminucation to search out the Eevee. Once there you can use Skyla/Liepard/Scorched Earth to try and search out Welder to start putting lots of energy onto Flareon GX so it can repeatly use Bright Flame dumping Fire Energy into the discard for later. Ninetales Break can also put energy into the discard to help while dealing lots of damage at the same time.
Burning Energy can help you save resources to keep the pressure on the opponent to allow you to bounce it back from the discard pile back onto Ninetales Break or onto Flareon GX
Ninetales V can be used as a subsitute if you cannot use Flareon GX. Ninetales V also has the added benfit of being able to copy opponent's active pokemon moves.
You can replace the Marnie with copy of Ninetales V or Fire Energy. I chose to put it in because it's one of the only full arts I have and is a nice card to use.