Ok...
Galvantula is fine, except I'd suggest using a Focus Sash to guarantee getting Sticky Webs up. However, Ribombee is faster so can outspeed more threats after setting Webs. Here is the set I would use:
Ribombee @ Focus Sash
Ability: Shield Dust
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
IVs: 0 Atk
- Sticky Web
- Bug Buzz
- Moonblast
- Defog
Defog gives you hazard removal which is desperately needed, however it does remove Sticky Web as well so bear that in mind.
Scizor usually prefers to be either Choice Banded or Scizorite because of the extra power. I would personally use Mega Scizor as it has better defensive stats:
Scizor-Mega @ Scizorite
Ability: Technician
EVs: 248 HP / 252 Atk / 8 SpD
Adamant Nature
- Swords Dance
- Roost
- Bullet Punch
- Knock Off
Mega Scizor doesn't need any speed investment, because Bullet Punch has priority.
Because you have Mega Scizor, Mega Heracross ---> Scolipede because it's ability Speed Boost means it gradually gets faster and so lets it outspeed and KO key threats to your team such as Quiver Dance Volcarona and/or Charizard.
Scolipede @ Poisonium Z
Ability: Speed Boost
EVs: 252 Atk / 4 SpD / 252 Spe
Jolly Nature
- Protect
- Megahorn
- Poison Jab
- Rock Slide
Poisonium Z for a one-time Nuke to stuff like Serperior.
Heracross is fine, except it usually prefers to be Choice Scarfed to outspeed things.
Masquerain is almost useless, its too weak and it's only selling point is its Intimidate. Use Choice Specs Yanmega instead for its POWA:
Yanmega @ Choice Specs
Ability: Tinted Lens
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
IVs: 0 Atk
- Bug Buzz
- Air Slash
- Giga Drain
- Psychic
Tinted Lens > Speed Boost because you already have a Scolipede, and also so that Yanmega doesn't need to worry about which move to click, knowing it will be neutral.
Volcarona doesn't need leftovers, give it Charti Berry to hopefully take a Rock-type attack. Also, make the EV spread 252 HP / 252 Def / 4 Spe with a Bold Nature to be as tanky as possible.
Hope I helped!