I've got a new team, I practiced against my friend who has every single Pokemon. I think this team is really good.

I still need help for perfection, though.
Yanmega
Modest Nature
Item: Focus Sash/Wise Glasses/Expert Belt
Ability: Speed Boost (AWESOME SKILL)
Moves:
Hypnosis
Bug Buzz
Protect
Air Slash
Decent, but it really needs modest nature, and psychic won't come in much handy. Hypnosis is better, but if you know how to use hidden power, then you could use Ice or Ground, but I still say hypnosis is best.
Charizard
Adamant/Jolly Nature
Item: Salac Berry (Ups speed when 1/4 or less HP)
Ability: Blaze
Moves:
Earthquake
Belly Drum
Fire Punch/Fang (punch is preferable, but needs emerald)
Substitute/Endure
Sorry, but I kinda demolished your set. If you really want charizard, then this is the best set, but if you are to use sub (the better of the two options) your max HP must be divisable by 4. The idea is to use Belly drum first (if you can), then sub to activate Salac Berry to sweep your opponent's team.
Lapras
Quirky Nature
Ability: Water Absorb (Perfect to against Water Types)
Moves:
Surf
Ice Beam
Thunderbolt
Psychic
Sorry again, but as far as defensive waters (or bulky water, as they are called) lapras is near the bottom of the barrel, may I suggest another? The commonest ones are Swampert, Milotic, Slowbro and Suicune.
Snorlax(Daddy)
Careful Nature
Ability:
Thick Fat (sorry, it's better)
Item: Leftovers
Moves:
Rest
Sleep Talk
Body Slam
Fire Blast(for skarmory)/Earthquake(for other steels)/Crunch(for ghosts)
Snorlax is a good tank, and a good restalker. Sleep talk uses one of it's moves at random when asleep.
Tyranitar
Modest Nature
Ability: Sand Stream (Is a pain once this Pokemon faints...)
Moves:
Dark Pulse
Brick Break
Earthquake
Rock Slide
Take him out, I'm sorry, but for tyranitar, you need AT LEAST 3 pokes immune to sandstorm. I noticed it's a sort of mixed sweeper and the best out there is definetly infernape, with Hasty/Naive, Life Orb, Flamethrower, Close Combat, Grass Knot, Thunderpunch/Nasty Plot/Stone Edge/Hidden power Ice.
Ambipom(I didn't need to use this little guy in battle at all.)
Modest Nature
Ability: Technician (I guess this too, is useful)
Moves:
Iron Tail
Brick Break
Aerial Ace
Thunderbolt
I see what you mean, and as much as I like ambipom, there's no room for him. One think that struck me with this team right away is its MASSIVE stealth rock problem, Yanmega and charizard lose 50% of there health as soon as they switch in, so I recomend a spinner. The best spinners are Donphan and Forretress (bot physical walls)
All comments and suggestions are NEEDED. I was to try and perfect this team. (If I should get rid of Ambipom, tell me so.)