Moves are now physical (melee) and speciel (elemental/ranged). That is the biggest thing, cause this useally means inn 9 out off 10 cases that using Fireblast on you're fightning type pokemon aint worth it, cause its Sp. Atk state is to low, to let it hit for much. So only use physical attacks for physical pokemons, UNLESS the pokemon has 100 atk and sp. atk - Then multi-attacks can work (Good examples are most Legendaries, Lucario).
You're hole team you play the game trough...enjoy that team for what it is, cause once you're done completing the game, there essentially useless.
This is where you haft to decide if you even care about pokemon games much, and want to continue. Building a good-trained team is atleast 20-50 hours work the first time. You first get like 100 battle points witch are easy enough to get, just takes time, to buy EV-items. Then you begin breed pokemons for right nature and so on, and then you equip hold item for EV training, and kill about 30 pokemons that gives to +atk. This is very simplified version.
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Lucario Sweeper @ Hold item.
http://www.smogon.com/bw/pokemon/lucario
Trait: Inner Focus
IV’s: Above average potential + Attack.
EVs: 252 Attack / 252 Speed
Nature: Adamant
- Swords Dance
- Close Combat
- Extreme Speed
- Ice Punch
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This is an example of my Lucario. First of all it got an abbility (Some abblities are crap, other abblities are game-breaking, and if you dont get X pokemon with its right abblity its pointless, other abblities makes you build the pokemon around it etc), its hidden-stats or just IV's are good for physical attacks such as Close combat, its EV's are trained for attack and speed, and the nature furthere increases attack state by 10% and lower its sp.Atk state by 10%.
Edit: Will suggest you read trough most pages inn this thread, many people included moi posted some stuff. I did a complete list of usefull pokemons for in-game teams, you can get easly while playing the game. I personally made a OK competive team just by using in-game pokemons, its very possibely to get a good team even for online stuff, by not going out of you're ways, trading etc.