The core evo chain is Erika's Victreebel which is a rare 3-part string where EVERY Pokemon is strong.
Use Pokemon Trader/Erika's Maids/Pokemon Breeder to get to a Victreebel as soon as possible.
Fragrance Trap and one-shot low hp Pokemon, or prep a Flash Touch and use Gold Berries to go toe-to-toe with higher hp opponents.
Ledian to Baton Pass and Erika's Bellsprout Soak Up to shift energies around quickly/unexpectedly to ramp quickly.
Pokemon Flute + Fragrance Trap and Razor Leaf to get some relatively cheap/free KOs if you only need a few more for a win to close it out.