Use Professor Burnet to discard the dragons you need then attack with Regidrago to use their attacks.
Our main damage dealers are the following:
Garchomp & Giratina GX if your opponent is already damaged, Giratina Vstar if you are willing to loose some energy, Koraidon EX which can deal lots of damage and even more if it has damage counters on it, M Charizard EX is your highest base damage and can also fuel your discard with more dragons if you get lucky and Rayquaza VMax which can deal massive damage if you discard energy.
Our support dragons are the following:
Ultra Necrozma which can both deal decent damage and also discard energy, Noivern EX which can stop your opponent fom playing Stadiums and Special Energy and protect from damage, Altaria EX which can protect from secondary effects of attacks, Hisuian Goodra VStar which reduces damage taken and Dragonite which can accelerate energy very quickly whilst dealing decent damage.