A standard moveset for Salamence, as Hypershell said, would be Earthquake, Outrage, Fire Blast, and Dragon Dance, although you have to breed to get Dragon Dance so you might want to consider Double Team or something.
Sceptile is a Special Sweeper it'd probably be a good idea to teach it Energy Ball, Focus Blast, Dragon Pulse, and Synthesis. The problem with Sceptile is he only has those 3 special moves that he can learn plus he'll still have trouble against Flying and Fire pokemon.
My recomendation it to swicth him out with a Tortera because most of your pokemon are built for Speed and he has a great physical attack power, physical defense, and a move set that can be adjustable and cover a lot of his weaknesses. Not to mention he gets a STAB Earthquake and Wood Hammer, and he has good HP and Defense so he could survive it and the next attack. Wood Hammer, Earthquake, Stone Edge, and Synthesis is what I would do but I recomend staying away from Ice types.
Blaziken, oh god how I love my Blaziken. This guy was made for type veraity: Flare Blitz, Earthquake, Shadow Claw, and Sky Uppercut. You could switch out Shadow Claw for Stone Edge if you're deftly afraid of Flying types but chances are that said Flying type would be much faster than him so I wouldn't recomend it plus it's great for taking out a Gardevoir since it's slow and has some bad Physical Defense.
Swampert's not exactly my cup of tea but he's still a good pokemon. Pretty much the same move set as my Feraligatr only his Earthquake is STAB too. Aqua Tail, Earthquake, Ice Punch, Mirror Coat. Now this is a lot of work! It can't learn Aqua Tail, Ice Punch and Mirror Coat naturaly. First you need to breed a female Swampert, or other pre evolve form, with a compatible male pokemon to get Mirror Coat or go to the Battle Frontier. Second you need to spend a lot of time at the trainer House and Battle Frontier to get BP for the other moves and you need a total of 104, I have no idea how much Mirror Coat is but it'll add to the 104.
Crobat not one that I would work with but he has some very decent moves. Cross Poison, Brave Bird, X Scissor/U Turn, Steel Wing/Agility/Double Team. Now there's only a little work for this breeding a female with a male for Brave Bird and getting a heart scale for Cross Poison but at least it's not near imposible like with Swampert.
Jolteon is pretty easy to do as long as you stay far far away from Ground types. Thunderbolt, Shadow Ball, Signal Beam, Agility/Double Team Again go to the Battle Frontier to get Signal Beam but those are the only Special Moves it can learn.
Gengar is another pokemon I don't work with but I can figure something out. Shadow Ball, Thunderbolt/Thunder, Energy Ball/Dream Eater, Hypnosis/Rain Dance/Double Team. Well I guess you can use him to power up your own moves, I don't know I don't work with him.
Now for the Psychic type the best, in my opinion, are Espeon, Gardevoir, Gallade, and Hypershell's favorite Mewtwo. Espeon is basicly a clone of Jolteon except replacing Thunderbolt with Psychic, but hey it works for Will Gallent's Speed team since he has both.
Gardevoir is my obvious favorite because of it's High Special Defense and her move set can take out a Vaporeon and Mewtwo. Psychic, Shadow Ball, Thunder Bolt/Energy Ball, Light Screen. Basicly pick your poison Gardevior can also learn Trick Room but it's not really worth it.
Gallade is the same thing execpt you replace the first 3 moves with Psycho Cut, X Scissor, and Thunder Punch. He can learn Stone Edge but you might not want that since it only has 5 PP.
Mewtwo, Okay I have to admit he's probably the best pokemon for covering all his weaknesses. Psychic, Shadow Ball, Aura Sphere, Flamthrower/Fire Blast/any Support Move you want. Yeah I don't exactly know the best way to use a Mewtwo but the possibilities are endless for One on One. Ask Hypershell for more details.