MEGA:
CHARIZARD-MEGA (X) - Out of all your mega options (Alakazam, Abomasnow, Gallade, and Khangaskhan) Mega Charizard X fits best in your team because to me it looks like you’re running Hyper Offense, and this way your team would be pretty balanced in the sense that you have about the same amount of special sweepers and physical sweepers. Gallade is a very close second as an option, but Gallade is more likely to get outsped as it’s setup move is Swords Dance, which doesn’t raise speed. It’s also mandatory that you breed your Charizard until you find a one with max IVs in HP, along with all the stats you listed so you take minimum recoil damage from Flare Blitz and take hits better. As for Roost or Earthquake, I would recommend Earthquake for coverage because Charizard only has decent bulk, and you only invested 4 EVs in defense.
PINSIR-MEGA - Mega Charizard X is definitely a much better physical than this particular Mega Pinsir because your set runs Thrash, which is a terrible idea because if your opponent switched to something that resists Flying you’re screwed. If you aren’t willing to breed for Quick Attack, then use Close Combat instead. As for Thrash, if you don’t have enough friendship for Return, feed it a lot of bitter berries and then teach it Frustration.
Z-User:
NAGANADEL - The main problem I have with your set is that it uses Dragon Pulse with Dragonium Z. If you’re going to run Dragonium Z, give it Draco Meteor instead to nuke things really well.
GARCHOMP/MIMIKYU - So your Garchomp is alright, pretty standard. For Stealth Rock/Crunch, I would go for Stealth Rock because Crunch doesn’t offer much coverage anyways and because you don’t have another hazard setter on your team. (Although Garchomp is more of an offensive Stealth Rock user, not a hazard setter). For Stealth Rock/Stone Edge, I would choose Stone Edge because it hits the flying types that are immune to your STAB Earthquake. Garchomp is unusable with Sand Veil, if you can’t get Rough Skin you might as well release him because he adds nothing to your team ATM. If you do get rid of him, I would suggest Mimikyu instead with the standard smogon set:
Mimikyu @ Mimikyunium Z
Ability: Disguise
Adamant Nature
EVs: 252 Atk/252 Spe/4 SpD
- Swords Dance
- Shadow Sneak
- Shadow Claw
- Play Rough
Regular:
GRENINJA-ASH - Give Greninja the Choice Specs for more damage. The reason why almost nobody runs Scarf or Specs on regular Greninja is because Greninja likes to use a wide variety of moves because they all get STAB from Protean. However, this is not the case for Ash Greninja, so feel free to run Choice Specs. Replace Spikes for Ice Beam if you do decide to run specs.
VOLCORONA - Replace Flamethrower with Fiery Dance for that chance to raise special attack. (Fire Blast is another option) Replace Hurricane with Giga Drain for recovery and coverage. As for your item, I would go with a Focus Sash to gaurantee you get at least one Quiver Dance up.
Conclusion - Is this team good enough to get past 50 trainers in the Battle Tree? Answer: No it is not. Half of Pokémon battling is breeding, sos chaining, etc. If you aren’t willing to do that, and you enter with 4 IV Pokémon with bad abilities, you’re at a serious disadvantage. Please consider looking for perfect IV and ability pokemon on the future.