AoH, I'm about casual competitive.
And I only do triple battles.
I use my favourites. But I usually try to get good IVs and natures. And create movesets that complement each other.
Like if I have a pokemon with Swift Swim, I'll teach it Rain Dance, and surf, aqua ring, and some other stab move. Then I have a Pokemon that know Thunder next to it that counters the type disadvantage. Then I have a Pokemon with Hurricane on the last spot.