After many years, I decided to play Pokémon again, and I like a lot the competitive side. Anyway, I'm kinda new to the BW2 competitive play, and... following various online guides, I built my first team. I know pretty much the basic stuff of a competitive team, but I'd like some tips from experts. Hoping I could get some help here. Thanks in advance to any rater. Though, I'd like to change Gengar and Dugtrio, because I don't use them that much. About the first Pokémon that I send out of battle... It depends. If there are setuppers (except Deoxys-D), I'm going to use Breloom, if not, then I'm going to use Registeel.

Registeel @ leftovers
Ability: Clear body
EVs: 252 HP, 252 attack
Nature: Careful
Stealth Rock

Overview: Even though there are better tanks, I choosed Registeel, because It's one of my favourite Pokémon.
Strategy: Thunderpunch against any flying Pokémon (except Landorus), earthquake against Magnezone. Stealth rock/toxic if the foe is switching

Gyarados @ Leftovers
Ability: Intimidate
EVs: 56 HP, 248 attack, 204 speed
Nature: Adamant
Aqua tail
Stone Edge
Dragon Dance

Overview: Gyarados probably is one of the most dangerous Pokémon in the entire metagame in my opinion. Thanks to its wonderful types, It's able to block any ground, water, steel and fire attack. It's the perfect counter against Heatran in my opinion.
Strategy:Aqua tail is probably the strongest physical water move, which is able to take down many Pokémon without problems. Earthquake... Well, it helps a lot against steel Pokémon... Stone edge... Well, I use it against flying and bug Pokémon, and as last... Dragon Dance. I use it principally when I'm sure that the foe is going to switch Pokémon (for example... Heatran).

Heatran @ Choice scarf
Ability: Flash Fire
EVs: 252 Special Attack, 252 Speed
Nature: Modest
Fire blast
Hidden Power Ice
Earth power
Flash Cannon
Well... Hum. Heatran is a quite used Pokémon in OU metagames, because of its ability to block a lot of attacks and... Well... W/e. Mine is a revengekiller. Mostly.
Strategy:What's to say about it, It's a hit'n switch Pokémon. Which needs to be switched every time I kill a foe Pokémon. Fire blast is its STAB move, so I can take down a lot of Pokémon without problems. HP ice helps me a lot against Dragon Pokémons (especially Salamence and Hydreigon). Earth power... Well, dunno. And Flash Cannon helps me against Pokémon like Tyranitar and such, in cases I haven't got more choices.

Dugtrio @ Choice band
: Arena Trap
EVs: 252 Attack, 252 speed
Nature: Jolly

Stone Edge
Sucker Punch
Shadow Claw
Overview: I dunno what to say about it, considering that I use it rarely.
Strategy:None so far, It's the least used Pokémon in my team. I use it only if the foe is about to use thunder, volt switch and such.

Breloom @ Toxic Orb
Ability: Poison heal
EVs: 252 attack, 252 speed
Nature: Adamant
Focus punch
Stone edge
Overview:Breloom is a pretty underated Pokémon, even though It's a great counter against slower Pokémon.
Strategy:Breloom is a great counter against setuppers, due to the "hide'n bite" tactic. Nothing much to say here. Spore, substitute, focus punch. Repeat over and over. Except when the other Pokémon has Magic bounce.

Gengar @ Leftovers
Ability: Levitate
EVs: 252 attack, 252 speed
Nature: Timid
Hidden power ice,
Shadow ball
Overview:Gengar is probably the best variant of Starmie and Alakazam. I put it in my team principally because it blocks any earth and fighting move (alongside with Gyarados).
Strategy: Substitute when I'm PRETTY sure that my foe is going to switch, HP ice to take down grass and ground Pokémon in cases Gyarados and Heatran are K.O. Thunderbolt against flying and water, shadow ball... Well, obviously against Psychic Pokémon. Though, I don't use Gengar that much, even if sometimes it reveals itself useful.