Get a strong Pokemon to send out first with not many weaknesses and strong moves and stats. I Highly would do a fast Pokemon with good Defense stats. LIKE Garchomp OR Slow Bulky Pokemon LIKE Snorlax , Metagross , Vaporeon,
have moves like extremespeed , bullet punch , Aqua jet , mach punch , ice shard , ........ So that you can finish your enemy's Pokemon off if your other Pokemon did not get the job done.
3.Have a Balance team. Have Fire moves , Water moves , Grass moves , ice moves , electric moves , Steel moves, Fairy moves , Fighting moves , and Ground Moves.
4 . Have at least 2 Bulky tanks on your team. LIKE Snorlax , Goodra , OR Lapras , Snorlax , OR Lapras , Goodra , . Have at least two Sweepers on your team LIKE Garchomp , Excadrill , Heracross , ...... and Have At least 2 mixed Pokemon ( Good ALL Around stats ) LIKE Kingdra , Blastoise ,Vensaur , Dragonite ,
5 . DO COMBO'S ...... like Yawn/Protect , Dragon Dance/Outrage , Calm mind/Psychic , Thunder Wave/Waterfall , Hone Claws/ Fly , Swords Dance/Outrage ,
6 . Always try to get Reflect And Light Screen Up to Double your Defenses.
HOPED I HELPED :)