I have to say picking a team isn't one of my strong points....so many to choose, so I'll recommend 6 types, choose one of each of these types as a start. Remember, only one of each element attacking per poke - thunder and t-bolt is very bad, though t-wave and t-bolt is fine.
1)An electric poke - only weak to ground.
2) A normal type - pretty solid, only one weakness.
3) A psychic - best for combatting fighters.
4) A water - generally very good, only 2 weaknesses.
5) A ground, ground/rock - use for a decent attacker, must have quake!
6) A fighter - use as normals are quite common.
Naturally, flyers, fires, grasses are all good, but this gives a general feel, and then you can tailor it however you want.
Pick your favourite from each type, and see how it goes. Hope this helps.
As for items, the best are IMO :
mira berry, leftovers, mint berry (with rest), scope lens, paralyz berry, and a good item attachment.
Best of luck, Raticata.
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A legendary is only legendary if it has a legendary set.