Mew-Leftovers-Psyshock, Dazzling Gleam, Surf, Calm Mind
Delta Venasaur-D. Venasaurite-Psychic, Moonblast, Thunderbolt, Calm Mind
Haxorus-Lucky Egg-Dragon Dance, Iron Head, Earthquake, Dragon Claw
Electivire-Magnet-Thunder Punch, Fire Punch, Low Kick, Earthquake
Giratina-Earthquake, Shadow Claw, Dragon Claw, Psychic (Swapping sometime)
Gengar-Expert Belt-Destiny Bond, Shadow Ball, Dazzling Gleam, Sludge Bomb
Okay, give advice please, tell me how to get better
Overall, I think this is a good team so I will give it 7 assuming that they are ev trained and have decent natures. I think you should get rid of gengar since you already have a better ghost type (giratina) and the poison type doesn’t do much apart from giving it more weaknesses and resistances that girantina probably has. I wouldn’t have haxorus hold a lucky egg since it only helps with leveling up and really u should be aiming to have all of your pokemon the same level. Since mew can learn any tm, I would change its moveset between battles. Maybe mew could have baton pass and calm mind/ swords dance? Also, I think that psychic is better that psyshock. If it is possible maybe mega eevee although i know it is hard to get your hands on an eevite without picking eevee as your starter to replace gengar. If it isn’t possible then maybe use ferrothorn cos u can get ferroseed in one of the hidden bases in the wiki. Then u could use it to tank hits whilst u heal ur team and set up entry hazards, inflict status conditions etc. Instead of electivire, I think that it might be better to have your electric type be a special attacker instead since there are more options available. Can I also ask why you are using haxorus? It does have quite a few weaknesses as a dragon type so might not be the best choice since there are quite a few ice types. I do not think that you would need a mega delta venusaur as mew can learn all of the moves in that specific moveset by tm and you will have gotten all of the tms with the exception of moonblast which can be substituted for dazzling gleam. If you want a physical attacker I would suggest blaziken since you can pick up its mega stone on victory road and there are quite a few ice type pokemon. If you do decide to use one i think it should have high jump kick, flamethrower/ fire punch/ flare blitz, swords dance and sunny day (I’m not very sure about this last one but it would get rid of weather conditions from the sandstorm and hail teams). If you do decide to keep haxorus i would give it a choice band or life orb. By the way, maybe on the teams that you feel confident about, you could swap some of your pokemon’s items for an amulet coin just to boost the money. Another thing is that maybe mega kangaskhan could work? It is good cos of the ability and does have decent attack
Edit: Now that I have started planning my own team for the E4 I see why haxorus was used although i think dragonite is better because of the moves that it can learn