Concierto Fusion Strike

The Fusion Strike archetype was the first one I played consistently, and to relatively good results, when I begun playing the Pokémon TCG, but even though I love Mew VMAX, giving up three prices and being weak to one of the most powerful types in the game made it more appealing to play a deck that ditches the first gen Mythical away, in order to give the fifth gen one the spotlight. 

This is built upon from a friend's base, and it uses the engine that makes the archetype so good:

The Fusion Strike archetype was the first one I played consistently, and to relatively good results, when I begun playing the Pokémon TCG, but even though I love Mew VMAX, giving up three prices and being weak to one of the most powerful types in the game made it more appealing to play a deck that ditches the first gen Mythical away, in order to give the fifth gen one the spotlight. 

This is built upon from a friend's base, and it uses the engine that makes the archetype so good: Genesect, who could work as an emergency attacker, but will mostly be dancing in the background handing you the cards you need via Fusion Strike System or Star Alchemy;  Cram-O-Matic, to either get what you need straight out of the deck or thin out your hand for further draw; Power Tablet, to boost your single prize attacker's damage (maxing out at 400 with all 4 of them and all 4 Fusion Strike Energy in play); and the addition of Skwovet (which I think is mandatory, to prevent bricking and to see more cards via: Genesect -> Skwovet -> Genesect). So, your ideal board is: 3 Genesect, 2 Meloetta, Skwovet.

Meloetta's show consists of singing Melodious Echo with just one FSE attached, thanks to Dimension Valley's effect, which makes it easy to attack and also minimize the resource loss once it's irremediably KOed, meaning you can hit on your first turn going second for 210 by accelerating two FSE on 2 Meloetta or 1 Meloetta and 1 Genesect (which makes it immune to ability based ability lock) via Elesa's Sparkle (the supporter you'll most likely be using on each turn after recovering your FSE with Special Charge, hence the Custom Catcher, for gusting on the same turn, though, don't be afraid to use it for extra draw) and then attaching the third FSE from hand (just avoid placing 2 on the same Pokémon). 

In the case any FSE're prized, once you've taken the rest out of the deck, use Rotom Dex to switch them out.

Lastly, Secret Box is the ACE SPEC of choice, since it can easily hand you the full combo, while the deck is completed by the usual Expanded Toolkit (Pokémon Ranger, Guzma, N, Field Blower, Vs Seeker and Float Stone), and Pokémon search and recovery (Battle VIP Pass, Quick Ball and Rescue Stretcher).