[Essay]

Originally Posted by Fat Manitary

I tried to reduce at minimum the number of pokémon you have to catch

I don't want spoiler, just tell me what I can use

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Excadrill: Earthquake/Rock Slide/Swords Dance plus one between X-Scissor (TM), Brick Break (TM), Shadow Claw (TM), Iron Head (Move Tutor)
Ferrothorn: Leech Seed/Power Whip, plus Iron Head/Gyro Ball (really depend on his speed stat, Iron Head seems stupid but he probably hasn't the right nature and EV to go for Gyro Ball), plus one coverage move of your choice
Haxours: Dragon Claw, one between Dragon Dance and Swords Dance, one between Earthquake, Dig, Bulldoze (I don't remember if you've access to EQ TM), one between Brick Break (TM), Superpower (Move Tutor), Low Kick (Move Tutor)
Chandelure: Psychic (TM), Shadow Ball (TM), Dark Pulse (Move Tutor), Flamethrower (TM), you can get the Dusk Stone in the Strange House

contain minor "spoiler" (gym types, E4 types)

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For the next gym (Skyla) you don't need any other pokémon, the only SE attack you can take is STAB Bubblebeam. Swords Dance and Rock Slide will do the work.
Keep leveling Ferroseed, upon evolving he'll learn Power Whip and you need it for Marlon (Water gym) since he resist all the moves bar Bounce and strikes back really hard.
Haxorus is really strong (even if it shouldn't be a problem, keep in mind that Fraxure evolve at level 48) and will clean the Dragon gym for you.
Since I think you don't want to catch and train many pokémon, I strongly suggest a Chandelure (you'll get one in the Strange House): he can learn Psychic (TM), Dark Pulse (Tutor), Shadow Ball (TM) and 3 of the Elite four are basically covered (Psychic, Fighting and Ghost), plus Flamethrower (TM) for STAB coverage.
I don't remember if you have access to route 15 before E4 to get Earthquake TM, otherwise you're stuck with Bulldoze/Dig...anyway for Haxorus a good set I think can be Earthquake/Dig/Bulldoze, Dragon Dance/Swords Dance, Dragon Claw, Superpower/Low Kick (both Tutor moves).

Great, that's what I wanted. Anyway, do you think I should dump Hippopotas and resign from Sand Stream?
My idea was to keep Excadrill, Hippo, Haxorus (eventhough he won't benefit from sands storm, but he looks kinda cool ) and get Terrakion, who would counter fire types and also get SpDef bonus from sandstorm. And by the way - I am not so sure about Chandelure.
By the way, is it good idea to give every one of my pokemons EQ? :P