How should I build my team for the elite 4?

Lol, there are no tricks... just level your pokemon more, man up and play on the SET instead of SHIFT configuration and you`re done.

And try to fight them using their weaknesses against them, except for Cynthia that uses variated pkmns.

Level up your pokemon more. Most combonations work.

wat starter youn pick

Doesn't really matter what your team is for the Elite 4. Just have different types available to exploit the weaknesses of the Pokemon and you're good to go. And of course level up enough.