Mega Charizard Y

Mega Charizard Y may not be as generally popular as Mega Charizard X, but due to how stats translate into Pokemon Go, it is the overall stronger variant. In fact, Mega Charizard Y rates among some of the top Pokemon in the game for raw DPS. This is one of the go-to options whenever Fire-type attackers are needed.

Mega Charizard Y's only real competition is Mega Blaziken. And, unfortunately, Mega Blaziken does out-DPS everyone's favorite fire-lizard. However, Mega Charizard Y's Flying sub-typing tends to allow it to pull ahead in the TDO battle, occasionally to such a large degree that it can actually surpass Mega Blaziken in terms of total average performance.

Best PvE Offensive Moveset

• Fire Spin is Mega Charizard Y’s best fast move and is strictly superior to Ember.

• Wing Attack is preferable to Air Slash and equal to Fire Spin if both have the same effectiveness.

• Blast Burn* makes Mega Charizard Y one of the absolute strongest Fire-type attackers in the game

• Overheat is Mega Charizard Y's best non-Elite charged move and beats Fire Blast and Flamethrower soundly.

• Dragon Breath and Dragon Claw can work as a pseudo-dragon attacker, but are best reserved for Mega Charizard X.
• Return has no purpose for Mega Charizard Y.

Fire Spin deals more damage with STAB, while Wing Attack offers slightly more energy generation. Either can work depending on preferred coverage. Dragon Breath is a powerful move, but lacks STAB, and falls behind vs neutral opponents. 

Blast Burn is a limited to Community Day events and Elite TMs, but is an incredibly powerful move, highly energy efficient, and almost mandatory for optimal use of Mega Charizard Y. Dragon Claw costs less energy, and can be used frequently.