Help Battling my Friends

Hey Guys, I'm unsure where to put this, so I'll put it here. :)
Anyways, at school, my friends and I always bring our Ds's so we can all play pokemon together, I have a good team and will usually win, but I want to add a bit more diversity to my team so I can play my friends better. I don't care about EV's or IV's, we don't use those, I'd only like to know what Items and Moves to use, more specifically, more pokemon. Here's my current team:

Serperior@Leftovers
-Leaf Blade
-Iron Tail
-Growth
-Leech Seed

Haxorus
-Dragon Dance
-Dragon Claw
-X-scizzor
-Shadow Claw

Darmanitan
-Fire Punch
I'm very sorry...... :/ I forgot his moveset from there......I really haven't used him in a while

Crobat
-Poison Fang
-Cross Poison
-Confuse Ray
-Fly

Starmie
-Surf
-Ice Beam
-Psyshock
-Recover

Scrafty
-Thunderpunch
-Hi Jump Kick
-Brick Break
-Crunch

I'm thinking of getting an Eevee and Evolving into Jolteon for Electric Coverage, I'm thinking of getting a Gigalith for Rock-Type awesomness, I want to get a good ground type pokemon for Jolteon to Team with In Double Battles, and I want a good Trick Room user for my slower pokemon.

So, that's it, I'd love to see your guys opinion on what pokemon I should add to my team, I can't wait for Replies and thank you in advance.

For this section of the forum, it might be useful to share your Pokemon EVs, abilities and natures. Looks more like an in-game team to me.

Anyway:

Physical Serperior is best of using Coil to boost its Attack, Defense and Accuracy. If it's not using Special moves, Growth's +1 in Special Attack is pointless:
-Coil
-Leaf Blade
-Aqua Tail (is a B2/W2 tutor move. It also has better coverage than Iron Tail)
-Return/Substitute
Nature: Jolly
EVs: 4 HP/252 Atk/252 Spe
Item: Leftovers

Haxorus has better coverage options than Shadow Claw and X-Scissor:
-Dragon Dance/Swords Dance
-Outrage
-Earthquake/Superpower
-Aqua Tail/Superpower/Dragon Claw/Dual Chop
Nature: Adamant
EVs: 36 HP/252 Atk/220 Spe
Item: Life Orb/Lum Berry
Ability: Mold Breaker

Darmanitan has a pretty good physical movepool to take advantage of:
-Flare Blitz
-U-turn
-Earthquake/Superpower
-Rock Slide
Nature: Adamant/Jolly
EVs: 4 HP/252 Atk/252 Spe
Item: Life Orb/Choice Band/Choice Scarf
Ability: Sheer Force

While Crobat's physical movepool is rather shallow, this is the best it can do offensively:
-Brave Bird
-Cross Poison/Super Fang
-U-turn
-Roost/Sleep Talk
Nature: Jolly/Adamant
EVs: 252 Atk/4 SDef/252 Spe
Item: Choice Band

Starmie doesn't really need Psyshock for a 3 attacks + Recover set; Thunderbolt can be used in its place for BoltBeam coverage. The preferred nature and EV spread are 252 SAtk/4 SDef/252 Spe with a Timid nature; the preferred ability is Natural Cure.

Scrafty is better off as a setup attacker to compensate for its average Attack:
-Dragon Dance
-Hi Jump Kick/Drain Punch
-Crunch
-Ice Punch/Taunt/Zen Headbutt
Nature: Jolly
EVs: 252 Atk/4 SDef/252 Spe
Item: Life Orb/Lum Berry
Ability: Moxie

or
-Bulk Up
-Drain Punch
-Crunch/Dragon Tail
-Rest
Nature: Careful
EVs: 252 HP/4 Atk/252 SDef
Item: Leftovers
Ability: Shed Skin

Don't bother with Gigalith; its movepool is very shallow and its defensive typing is bad. Jolteon is a decent Pokemon, tbh:
-Thunderbolt
-Volt Switch
-Hidden Power (Ice/Fire)
-Signal Beam/Shadow Ball
Nature: Timid
EVs: 252 SAtk/4 SDef/252 Spe
Item: Life Orb/Choice Specs
Ability: Volt Absorb

Reuniclus is a good Trick Room user to add in:
-Trick Room
-Psychic/Psyshock
-Shadow Ball
-Focus Blast
Nature: Quiet
EVs: 192 HP/64 Def/252 SAtk
Item: Life Orb
Ability: Magic Guard