XY/ORAS Singles Some Advice Please~?

[AzureEdge]

So, I'm a bit new to competitive battling, and I would like advice in the move sets, and the item sets, because I'm not very good at choosing those. I'm also not sure if I should take out Cofagrigus or not and replace it with a Greninja. Thank you~! (P.S EV'S are not Final yet, although irregular, I'm just testing it out )

Claydol @ Earth Plate
Ability: Levitate
EVs: 252 HP / 4 Atk / 252 SpA
Mild Nature
IVs: 0 Spe
- Dazzling Gleam
- Earthquake
- Gyro Ball
- Charge Beam

Eelektross (M) @ Big Root
Ability: Levitate
EVs: 140 HP / 108 Atk / 76 Def / 84 SpA / 12 SpD / 88 Spe
Quiet Nature
- Drain Punch
- Volt Switch
- Flamethrower
- Giga Drain

Shiftry (M) @ Big Root
Ability: Chlorophyll
EVs: 252 HP / 156 Def / 4 SpA / 96 Spe
Timid Nature
- Leech Seed
- Giga Drain
- Solar Beam
- Sunny Day

Luxray (M) @ Berry Juice
Ability: Rivalry
EVs: 196 HP / 132 Atk / 112 Def / 4 SpA / 64 Spe
Lonely Nature
- Volt Switch
- Iron Tail
- Thunderbolt
- Night Slash

Seismitoad (M) @ Mystic Water
Ability: Water Absorb
EVs: 140 HP / 116 Atk / 196 Def / 4 SpA / 32 Spe
Adamant Nature
- Earthquake
- Hydro Pump
- Ice Punch
- Sludge Bomb

Cofagrigus (M) @ Mind Plate
Ability: Mummy
EVs: 164 HP / 4 Atk / 156 Def / 184 SpA
Rash Nature
- Shadow Ball
- Zen Headbutt
- Night Shade
- Grass Knot

If I did switch Cofagrigus with Greninja here is the one I'll be using.
Greninja (M)
Ability: Protean
EVs: 168 HP / 88 Atk / 252 Def
Adamant Nature
- Acrobatics
- Blizzard
- U-turn
- Shadow Sneak

 

[Shiny Motley]

Oooh boy, there's going to be quite a bit to talk about here but I hope you don't mind a bit of reading. XD I'm already discussing about EVs with you, so I'll leave that part out. Also, I'd suggest reading through here to get a gist of how to team build; yes, the data is a little outdated, but it is still a very good and thorough guide about what you should do when making a competitive team.

Secondly, items that boost only one type of move (so plates and mystic water, for example) are usually better off replaced by something else. For attackers, this usually means Life Orb or any of the Choice items and, situationally, can also include Wide/Zoom Lens, Expert Belt, Power/Mental/White Herb, etc.

If you want to help out your bulkier Pokemon, Assault Vest, Sitrus Berry, and Leftovers/Black Sludge are the way to go, for reliable healing. Big Root, while it does increase the amount of health gained from draining moves, can be rather unreliable at times. Berry Juice just doesn't heal enough compared to Sitrus Berry, and Leftovers, in the long run, can be immensely useful and is usually the go-to item for defensive Pokemon. Another item you can consider is the Rocky Helmet, usually only used for physically tanky Pokemon, though none of your Pokemon seem to be capable of using it so far.

Now onto the Pokemon. If you're running Gyro Ball on Claydol, I'd suggest a speed-lowering nature along with 0IVs, to maximize both power and bulk. That said, I usually don't recommend mixed sets unless you can pull it off well or the Pokemon is made for mixed sets, but if you think you can do it, fine with me.

I'm not sure how to deal with Eelektross, Shiftry, and Seismitoad, so I'll skip those for now.

Regarding Luxray, Rivalry is a terrible ability to have and I'd suggest either Guts or Intimidate over it, depending on if you want to go for more offense-oriented or bulkier. Ice Fang is almost an absolute must to deal with pesky ground types imo, but people will likely disagree with me.

Cofagrigus has piss-poor Attack power. In addition, Cofagrigus would like to keep its defenses up since it's been blessed with decent defenses both ways. You could go with a really good set up here with hazards like Spikes or Toxic Spikes, depending on preferences, and Pain Split would be able to help keep Cofagrigus healthy while also hurting your opponent. You can further cripple the opposing team with Will-o-wisp, though I wouldn't suggest having that if you choose to use Toxic Spikes.

As for Greninja, if you're going for Adamant Nature (which I wouldn't, I'd suggest Jolly over Adamant if you want to speed tie other Gren's), then you should drop Blizzard for something else. Coverage moves you can consider include Low Kick, Ice Punch, Night Slash, Rock Slide, and Waterfall. If you want to use a sort of lead or scout, you can also try running Taunt and Spikes/Toxic Spikes on it.

Your team in general looks like a good grass type could give you quite a bit of problems, especially Mega Venusaur and kin. I'd suggest you rethink some of your team a bit and try again ^^;