For people looking for a strong build, your starters are actually, mostly, a one man army. Pikachu can do everything, and Larvitar (later Tyranitar) is a perfect tank, weaknesses he is slow, vulnerable to Water, Ground, Fighting and Steel. Or you take Bagon (Later Salamence) Very fast and high damage, vulnerable to Ice, Rock and Electric.
Best Moves (Tyranitar): Fire Punch (Or Superpower), Crunch, Stone Edge, Earthquake.
Best Moves (Salamence): Dragon Dance, Outrage, Earthquake, Fire Blast (Or Roost if you think your Salamence cant tank the attacks).
I cant say if all of this is possible in the game, this is tournament knowledge, not ingame knowledge.