Ok long story short, XnY is my first pokemon game. Ive been a poorfag since forever and finally landed a sweet ass job and the rest is just so much disposable income.

Ive got 6 badges without an issue but now seem to be worrying about team-optimisation
IE: is my team lacking certain types?
will certain pokemon fuck my team sideways?
Am i missing certain roles within my team?
Are my natures/abilities/movesets wrong?

Now dont get me wrong, I love this shit, the complexity of building a working team in the world is what draws me to the game but I really dont know where to begin.
Should I be aiming to be super effective against all types?
What team roles should I be aiming to fill?
>So far i think i need a tank, a support and a few damage whores

TLDR: What are the absolute essentials in building a successful team?

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