Sceptile: You can go P. Attacker or S. Attacker; Crunch, Leaf Blade, Dragon Claw and Double Team/Leech Seed usually works well for me. If you have access to Emerald, Thunderpunch is also good. Or you can use Swords Dance with Aerial Ace and Brick Break.
Tentacruel:
~Surf/Hydro Pump
~Giga Drain
~Ice Beam
~Barrier/Confuse Ray/Toxic/Mirror Coat/Haze (Something to help it with the low Defense, or just increase usefulness)
You COULD try RestTalk on Tentacruel, but from its low Defense, it may or may not work well for you :/
Salamence: You could go P. Att if you have access to Emerald/have plenty of TM's, or Sp. Att if you don't.
~Dragon Dance
~Earthquake
~Rock Slide/Brick Break/Fly/Aerial Ace
~Rock Slide/Brick Break/Fly/Aerial Ace
~Crunch
~Fire Blast
~Hydro Pump
~Dragon Claw
Skarmory: Best utility in Gen III
. Spikes/Whirlwind is what people use it the most for, with or without RestTalk. If you're just playing it in-game, then I suggest this
~Steel Wing
~Drill Peck
~Return
~Spikes/Toxic/Curse
Gardevoir:
~Calm Mind
~Psychic
~Thunderbolt
~Will'o Wisp/Ice Punch
Camerupt:
~Earthquake
~Rock Slide
~Flamethrower
~Eruption/Protect/Return/Body Slam