Gothitelle

Gothitelle is a mediocre Psychic Type swimming in a sea of mediocre Psychic Types. It's not the absolute worst, but it's substantially behind the competition.

Best PvE Offensive Moveset

• Confusion is the offensive Fast Move of choice, out-playing Charm on every relevant front.
• Psychic is the Charged Move of choice, while Future Sight is a pretty poor runner-up.
• Rock Slide is an easy skip.

Best PvE Defensive Moveset

• Charm and Confusion are both good on Defense. The latter is stronger here due to STAB, but both have their use depending on your Charged Move choice.
• Rock Slide works with either Fast Move.
• Psychic works well with Charm
• Future Sight is a pass.

Confusion provides superior energy gains and hits quite hard with STAB. Charm has pitiful energy generation, but offers niche typing coverage. 

Rock Slide costs the least amount of energy, provides wide coverage, and is overall a solid and efficient move. Psychic and Future Sight are the only other options available; the former costs 10 less energy while the latter deals considerably more damage.