Take a quite strong fully evolved pokemon and try to build an early gym (from 1st to 3rd) with it without making it too powerful (TM rewards are not important just the team)

2nd gym
Fairy

lvl 18 MimeJr.
Ability: Filter
Moves: Confusion, Teether Dance, Reflect, Mimic

lvl 20 Slurpuff
Ability: Sweet Veil
Moves: Draining Kiss, Round, Fake Tears, Cotton Spore