Get a different Luxray, get a Jolly one. Naive is a SPC defense reducing nature, you may not want to lower that. Lower your special attack, since your moves are physical.
Gengar has Dream eater, but no one on your team knows a sleep inducing move.
Modest Gengar has Payback? I guess...thats ok, since it doubles your power if you move last. But Gengar's got some good speed, so you'll have an ATK reducing nature with a physical move that will rarely get the double power boost.
Shadow punch? Thats another physical move you put on your Gengar...this Gengar needs to be rethought out completely.
neutral Try this, keep shadow ball. thats a special move, plus it has that extra STAB damage since Gengar is a Ghost type, using a Ghost move.
Another move could be Focus blast, to rid those annoying Dark types who may try to defeat your Gengar.
Some other moves could be Thunder/Thunderbolt/Psychic/Energy Ball/Dark pulse.
If you insist on keeping Dream Eater, then at least have Hypnosis to go along with it. It's a worthless move if you have no sleep inducing moves.
As for the Salamance, my personal opinion is. Impish is a horrible nature to have. I'd go either Adamant or Jolly. I think Jolly may be a better choice.
Also Dragon Breath on Salamance? Maybe replace it with Dragon Pulse?
Here, check out my Salamance. Jolly and EV trained in ATK and SPD.
Fire fang, Outrage, Earthquake and Dragon dance.
If they put in a Pokemon you know you'll have no issues with at all. Use a Dragon Dance to further boost your speed and attack. It'll give you an edge.
All of those attacks I have are physical ones, which are more worth having with an ATK EV trained Pokemon.
Also I agree with what the person above me said.
Maybe try these moves on your Swampert.
Earthquake - STAB damage!
Waterfall - STAB damage!
Stone edge
Avalanche
reason I chose Avalanche is to replace that ice move you had there. And since Swampert is quite slow, and Avalanches power doubles if you move last. It'll basically be a 100 atk move. Which is 25 atk greater than ice punch.
Adamant is ATK boosting nature, keep that in mind. You need atk moves.
Heres a website that shows you the natures and their boosts and negatives.
http://www.legendarypokemon.net/natures/ And as for your other Pokemon, I have no idea.
sweatdrop