Team Rate =)

[MisterDecent]

Hey all, it's been a while since i posted at GW.
Anyways, here's my Pokemon Platinum team-

Gallade Lv 100
Careful Nature
-Drain Punch
-Psycho Cut
-Leaf Blade
-Stone Edge

Magmortar Lv 100
Gentle Nature
-Overheat
-Thunderbolt
-Solar Beam
-Sunny Day

Empoleon Lv 100
Careful Nature
-Ice Beam
-Flash Cannon
-Surf
-Earthquake

Drapion Lv 100
Jolly Nature
-X-Scissor
-Poison Jab
-Ice Fang
-Dark Pulse

Garchomp Lv 100
Quirky Nature
-Dragon Claw
-Earthquake
-Shadow Claw
-Swords Dance

Yanmega Lv 100
Rash Nature
-Air Slash
-Bug Buzz
-Shadow Ball
-Psychic

Suggestion of items to be held or change in movesets/natures would be appreciated, Thanks in advance :)

[Seerow]

Ideally you want to get rid of Earthquake on Empoleon and teach it a special move, because its special attack is naturally higher. Grass Knot works. Flash Cannon isn't terrific either because Steel attacks get terrible type coverage. You could teach it something like Yawn or Toxic instead if you like.

Drapion wants a physical attack instead of Dark Pulse. Night Slash would be good.

Garchomp wants Fire Fang or Fire Blast instead of Shadow Claw, because Dragon, Fire, and Ground is an attacking combination not resisted by any Pokémon currently in the game. Failing that, Stone Edge is good. Shadow Claw isn't terrific with the other attacks, though. Also consider Outrage instead of Dragon Claw - not much can stand up to Outrage after a Swords Dance.

Gallade wants Close Combat instead of Drain Punch.

There are some other fixes I could make, but I won't right now, firstly because I'm lazy and can't be bothered, secondly because I'm presuming this team is for in-game purposes so it really doesn't matter much if you go through with terrible movesets, you can still beat the game easily enough. The general fixes I have given should be easily good enough to get through the game, but if you want more say so and I will give them.

[MisterDecent]

K, what about now?

Gallade Lv 100
Careful Nature
-Close Combat
-Psycho Cut
-Leaf Blade
-Stone Edge

Drapion Lv 100
Jolly Nature
-X-Scissor
-Poison Jab
-Ice Fang
-Night Slash

Garchomp Lv 100
Quirky Nature
-Dragon Claw (May Switch to Outrage)
-Earthquake
-Fire Fang
-Swords Dance

Empoleon Lv 100
Careful Nature
-Ice Beam
-Toxic?
-Surf
-Grass Knot

[Bulbasaurus Rex]

If you're going to replace Flash Cannon, then you should also replace Poison Jab on Drapion, as Poison (other than Toxic) is an even worse attacking type than Steel is.

[Seerow]

Fair point, I overlooked that. You may want to consider replacing Poison Jab with Earthquake. It might also be worth considering replacing X-Scissor with Swords Dance, since you have Night Slash to cover Psychics and Ice Fang to cover Grass, the the only thing X-Scissor covers that they don't is Dark.

[MisterDecent]

But shouldn't i keep Poison Jab due to STAB?
I'll switch X-Scissor with Swords Dance.

And any ideas for items?

[Bulbasaurus Rex]

You had STAB with Flash Cannon, too. The really poor type coverage (only super effective against Grass, which is covered by Ice Fang anyway) doesn't make it worth keeping even with STAB.

[MisterDecent]

So replace Posion Jab with Earthquake?
Now-

Gallade Lv 100
Careful Nature
-Close Combat
-Psycho Cut
-Leaf Blade
-Stone Edge

Drapion Lv 100
Jolly Nature
-X-Scissor
-Earthquake
-Ice Fang
-Night Slash

Garchomp Lv 100
Quirky Nature
-Outrage
-Earthquake
-Fire Fang
-Swords Dance

Empoleon Lv 100
Careful Nature
-Ice Beam
-Toxic
-Surf
-Grass Knot

Magmortar Lv 100
Gentle Nature
-Overheat
-Thunderbolt
-Solar Beam
-Sunny Day

Yanmega Lv 100
Rash Nature
-Air Slash
-Bug Buzz
-Shadow Ball
-Psychic