Should I improve my pokemon team?

I'm not sure whether I should change some of the pokemon or items in the team that I have.
My Current Team is:
Skarmory (Impish)
Item:Quick Claw
Ability: Sturdy
Spikes/Roost/Stealth Rock/Whirlwind

Arcanine (Hardy)
Item:Charcoal
Ability: Flash Fire
Crunch/Hidden Power(Grass)/Flamethrower/Extremespeed

Snorlax (Brave)
Item: Leftovers
Ability: Immunity
Body Slam/Earthquake/Rest/Sleep Talk

Milotic (Bold)
Item: Mystic Water
Ability: Marvel Scale
Surf/Ice Beam/Toxic/Recover

Darkrai (Serious)
Item: Blackglasses
Abilty: Bad Dreams
Night Shade/Dark Pulse/Dream Eater/Dark Void

Mew (Adament)
Item: Expert Belt
Ability: Synchronize
Psychic/Roost/Me First/Aura Sphere

I'm currently thinking of replacing mew with rayquaza, and I need ideas on how to improve my team (I'm pretty new to the EVs and IVs stuff since I just recently started building a team)
Any Suggestions?

Firstly, you are wasting some of Arcanine's potential. Arcanine is an attack-strong Pokemon, yet you are using a special attack (flamethrower). You need to replace flamethrower with the undoubtedly best attack-type fire move, flare blitz.

Get this: not only will flare blitz fill more potential with Arcanine (because flare blitz is an attack-type fire move), but flare blitz has both the same accuracy and PP as flamethrower. Here's the big difference: Flare Blitz has an attack power of a whopping 120, while flamethrower has a special attack power of only 95.

Now, the one drawback is that Arcanine will receive recoil damage. But, that is the only drawback. Honestly, given the rest of the positives of this move switch, you should consider switching, regardless.

I've actually considered switching Flamethrower to Flare Blitz, however my arcanine has low defense/sp defense, so I'm not really much of a fan of having recoil dealing moves on him. What's more, it's Sp.Att stat is pretty close to it's attack (Att: 132, Sp.Att: 125) so it's actually fine for me to stick to sp.atk based moves

Hey LittleChiro, I'm just going to move this over to In-Game Team Help, as Rate My Team threads don't belong in Fourth Generation Gaming. If you have any questions regarding Fourth Gen or where to post what, please feel free to ask me!

[ Moved ]

Sorry about that, new to this website. thanks anyway

Firstly, Darkrai should not have Night Shade, it can use other moves such as Thunderbolt and Ice Beam. Secondly, your Mew's moves don't suit its nature. As Adamant increases Attack and decreases Special Attack, having Psychic and Aura Sphere might be redundant, you can go for a physical moveset that contains Zen Headbutt, U turn or the elemental punches.

i can't decide which move to replace for darkrai's night shade yet, my mew is hp 252/ spatk 252 ev trained, that's why i had special moveset, it's stats currently is like 270hp /17X atk/ 15X def/ 17X sp.atk/ 15x spdef/ 14x spd

I'd recommend Focus Blast to replace Night Shade. Focus Blast is an excellent coverage move which hits many of the Dark and Steel-types that block Dark Pulse super-effectively.

sounds good, is there any other coverage? i realized my team lacks grass type moves